Twin scroll turbocharger in a variable displacement engine

ABSTRACT

Methods and systems are provided for operating an engine with variable displacement engine (VDE) operation coupled to a twin scroll turbocharger. One method comprises directing exhaust from a first outer cylinder and a first inner cylinder of four cylinders to a first scroll of the twin scroll turbocharger, directing exhaust from a second outer cylinder and a second inner cylinder of the four cylinders to a second scroll of the twin scroll turbocharger, and during a first condition, firing all four cylinders with uneven firing.

FIELD

The present disclosure relates to a turbocharger layout for a variabledisplacement engine.

BACKGROUND AND SUMMARY

Twin scroll turbocharger configurations may be used in turbochargedengines. A twin scroll turbocharger configuration may separate an inletto an exhaust turbine into two separate passages connected to exhaustmanifold runners so that exhaust from engine cylinders whose exhaust gaspulses may interfere with each other are separated.

For example, on a typical inline four (I4) engine with a cylinder firingorder of 1-3-4-2, exhaust manifold runners from cylinder 1 and cylinder4 may be connected to a first inlet of a twin scroll turbine and exhaustmanifold runners from cylinder 2 and cylinder 3 may be connected to asecond inlet of said twin scroll turbine, where the second inlet isdifferent from the first inlet. Separating exhaust gas pulses in thisway may result in increased efficiency of exhaust gas delivery to theturbine and may increase power output of the turbine.

However, the above configuration may not be applicable to an engine witha different firing order. As an example, ignition events in afour-cylinder engine may be configured to occur in the following order:1-3-2-4. In this scenario, coupling exhaust manifold runners fromcylinders 1 and 4 to a first inlet and coupling exhaust runners fromcylinders 2 and 3 to a second inlet of the twin scroll turbine mayresult in exhaust pulse interference producing a decrease in volumetricefficiency and affecting turbine spool-up.

The inventors herein have identified the above issue and devised anapproach that partially addresses this issue. In one approach, a methodfor the engine comprises directing exhaust from a first outer cylinderand a first inner cylinder of four cylinders to a first scroll of a twinscroll turbocharger, directing exhaust from a second outer cylinder anda second inner cylinder of the four cylinders to a second scroll of thetwin scroll turbocharger, and during a first condition, operating allcylinders with at least one uneven firing. An example engine maycomprise four cylinders arranged in an inline configuration with afiring order of 1-3-2-4, as mentioned above. Based on cylinder positionswithin an engine block, cylinder 1 may be categorized as a first outercylinder, cylinder 4 may be identified as a second outer cylinder,cylinder 2 may be categorized as a first inner cylinder (next tocylinder 1), and cylinder 3 may be identified based on its position inthe engine block as second inner cylinder (next to cylinder 4). Byseparating exhaust from cylinders 1 and 2 from exhaust flowing out ofcylinders 3 and 4, exhaust pulse separation may be maintained betweencylinders 1 and 4, and between cylinders 2 and 3.

As another example, a turbocharged variable displacement engine mayinclude four inline cylinders such that two cylinders are positioned asouter cylinders while remaining two cylinders are positioned as innercylinders. The engine may be configured to operate with a firingsequence of first outer cylinder-second inner cylinder-second outercylinder-first inner cylinder. To enable sufficient exhaust pulseseparation, exhaust runners from the first outer cylinder and the firstinner cylinder may be fluidically coupled to a first scroll of anexhaust turbine of the turbocharger while exhaust runners from thesecond inner cylinder and the second outer cylinder may be fluidicallycoupled to a second scroll of the exhaust turbine of the turbocharger.The engine be operated with uneven firing by firing the first outercylinder midway between the second inner cylinder and the second outercylinder, and by firing the first inner cylinder, the second innercylinder, and the second outer cylinder at 240 crank angle degreeintervals from each other. Thus, the first outer cylinder may be firedapproximately 120 crank angle degrees after the second outer cylinderhas fired, and 120 crank angle degrees before the second inner cylinderfires. The engine may also be operated in a variable displacement mode(or reduced cylinder mode) by deactivating the first outer cylinder andfiring the remaining three cylinders at 240 crank angle degreeintervals.

In this way, a turbocharged engine with a firing order of 1-3-2-4 may beoperated with exhaust pulse separation. By delivering exhaust fromcylinder 1 and cylinder 2 to a first scroll of an exhaust turbine anddirecting exhaust from cylinder 3 and cylinder 4 to a second scroll ofthe exhaust turbine, exhaust pulse interference during an uneven firingmode may be reduced. Each scroll of the exhaust turbine may receiveexhaust pulses separated by a minimum of 240 crank angle degrees in thefull-cylinder mode with uneven firing and the reduced cylinder evenfiring mode. Exhaust pulse separation with a twin scroll turbochargermay enable more efficient recovery of kinetic energy from the exhaustgases. Therefore, the engine may operate with increased power output andimproved fuel efficiency.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a schematic diagram of an example cylinder within anengine.

FIG. 2 portrays a schematic layout of a four-cylinder engine with a twinscroll turbocharger, according to an embodiment of the presentdisclosure.

FIG. 3 is an illustration of a crankshaft in accordance with the presentdisclosure.

FIG. 4 depicts an alternate exhaust layout for the embodiment shown inFIG. 2.

FIG. 5 shows a schematic diagram of an engine including a crankshaft, abalance shaft, and a camshaft, according to an embodiment of the presentdisclosure.

FIGS. 6-8 illustrate example spark timing diagrams in different engineoperation modes.

FIG. 9 depicts an example flowchart for selecting a VDE mode or non-VDEmode of operation based on engine operating conditions.

FIG. 10 portrays an example flowchart for transitions between differentengine modes based on engine operating conditions, according to thepresent disclosure.

FIG. 11 demonstrates example plots illustrating the selection of engineoperation mode based on engine speed and engine load.

FIG. 12 shows an example layout of the engine of FIG. 2 with anintegrated exhaust manifold.

FIG. 13 presents an alternate exhaust layout for the engine of FIG. 12.

FIG. 14 shows an embodiment of the engine of FIG. 2 with a cam profileswitching system that allows the engine to operate substantially in athree-cylinder mode.

FIG. 15 depicts an example valve timing for the embodiment of FIG. 14,according to the present disclosure.

FIG. 16 is an example flowchart for operating the example engine of FIG.14.

FIG. 17 illustrates an example flowchart for transitioning betweendifferent engine operating modes for the example engine of FIG. 14.

FIG. 18 depicts example transitions between the two VDE and the non-VDEmodes of engine operation.

DETAILED DESCRIPTION

The following description relates to operating an engine system, such asthe engine system of FIG. 1. The engine system may be a four-cylinderengine capable of operation in variable displacement engine (VDE) modecoupled to a twin scroll turbocharger as shown in FIG. 2. Thefour-cylinder engine may include a symmetric exhaust layout as shown inFIG. 2 or may have an asymmetric exhaust layout as shown in FIG. 4.Further, the engine may include a crankshaft, such as the crankshaft ofFIG. 3 that enables engine operation in a three-cylinder or two-cylindermode, each with even firing, as shown in FIGS. 6 and 8, respectively.The engine may also be operated in a four-cylinder mode with unevenfiring, as shown in FIG. 7. A controller may be configured to select anengine operating mode based on engine load and may transition betweenthese modes (FIGS. 9 and 10) based on changes in torque demand (FIG.18), engine load and speed (FIG. 11). Crankshaft rotation in the exampleengine may be balanced by a single balance shaft, as shown in FIG. 5,rotating in an opposite direction to that of the crankshaft. The enginesystem of FIG. 2 may be modified to include an integrated exhaustmanifold (IEM) with symmetric exhaust layout (FIG. 12) or asymmetricexhaust layout (FIG. 13). An additional embodiment of the engine (FIG.14) may include an engine capable of operating primarily in athree-cylinder VDE mode with reduced excursions into a four-cylindermode. Herein, engine operation in three-cylinder mode may compriseoperation with either a shorter intake duration or a longer intakeduration (FIG. 15). The controller may select the engine operation mode(FIG. 16) based on engine load and may transition between the availablemodes based on changes in engine load (FIG. 17).

Referring now to FIG. 1, it shows a schematic depiction of a sparkignition internal combustion engine 10. Engine 10 may be controlled atleast partially by a control system including controller 12 and by inputfrom a vehicle operator 132 via an input device 130. In this example,input device 130 includes an accelerator pedal and a pedal positionsensor 134 for generating a proportional pedal position signal PP.

Combustion chamber 30 (also known as, cylinder 30) of engine 10 mayinclude combustion chamber walls 32 with piston 36 positioned therein.Piston 36 may be coupled to crankshaft 40 so that reciprocating motionof the piston is translated into rotational motion of the crankshaft.Crankshaft 40 may be coupled to at least one drive wheel of a vehiclevia an intermediate transmission system (not shown). Further, a startermotor may be coupled to crankshaft 40 via a flywheel (not shown) toenable a starting operation of engine 10.

Combustion chamber 30 may receive intake air from intake manifold 44 viaintake passage 42 and may exhaust combustion gases via exhaust manifold48 and exhaust passage 58. Intake manifold 44 and exhaust manifold 48can selectively communicate with combustion chamber 30 via respectiveintake valve 52 and exhaust valve 54. In some embodiments, combustionchamber 30 may include two or more intake valves and/or two or moreexhaust valves.

In the example of FIG. 1, intake valve 52 and exhaust valve 54 may becontrolled by cam actuation via respective cam actuation systems 51 and53. Cam actuation systems 51 and 53 may each include one or more camsmounted on one or more camshafts (not shown in FIG. 1) and may utilizeone or more of cam profile switching (CPS), variable cam timing (VCT),variable valve timing (VVT) and/or variable valve lift (VVL) systemsthat may be operated by controller 12 to vary valve operation. Theangular position of intake and exhaust camshafts may be determined byposition sensors 55 and 57, respectively. In alternate embodiments,intake valve 52 and/or exhaust valve 54 may be controlled by electricvalve actuation. For example, cylinder 30 may alternatively include anintake valve controlled via electric valve actuation and an exhaustvalve controlled via cam actuation including CPS and/or VCT systems.

Fuel injector 66 is shown coupled directly to combustion chamber 30 forinjecting fuel directly therein in proportion to the pulse width ofsignal FPW received from controller 12 via electronic driver 99. In thismanner, fuel injector 66 provides what is known as direct injection offuel into combustion chamber 30. The fuel injector may be mounted in theside of the combustion chamber or in the top of the combustion chamber,for example. Fuel may be delivered to fuel injector 66 by a fuel system(not shown) including a fuel tank, a fuel pump, and a fuel rail. In someembodiments, combustion chamber 30 may alternatively or additionallyinclude a fuel injector arranged in intake manifold 44 in aconfiguration that provides what is known as port injection of fuel intothe intake port upstream of combustion chamber 30.

Ignition system 88 can provide an ignition spark to combustion chamber30 via spark plug 91 in response to spark advance signal SA fromcontroller 12, under select operating modes. Though spark ignitioncomponents are shown, in some embodiments, combustion chamber 30 or oneor more other combustion chambers of engine 10 may be operated in acompression ignition mode, with or without an ignition spark.

Engine 10 may further include a compression device such as aturbocharger or supercharger including at least a compressor 94 arrangedalong intake passage 42. For a turbocharger, compressor 94 may be atleast partially driven by an exhaust turbine 92 (e.g. via a shaft)arranged along exhaust passage 58. Compressor 94 draws air from intakepassage 42 to supply boost chamber 46. Exhaust gases spin exhaustturbine 92 which is coupled to compressor 94 via shaft 96. For asupercharger, compressor 94 may be at least partially driven by theengine and/or an electric machine, and may not include an exhaustturbine. Thus, the amount of compression provided to one or morecylinders of the engine via a turbocharger or supercharger may be variedby controller 12.

A wastegate 69 may be coupled across exhaust turbine 92 in aturbocharger. Specifically, wastegate 69 may be included in a bypasspassage 67 coupled between an inlet and outlet of the exhaust turbine92. By adjusting a position of wastegate 69, an amount of boost providedby the exhaust turbine may be controlled.

Intake manifold 44 is shown communicating with throttle 62 having athrottle plate 64. In this particular example, the position of throttleplate 64 may be varied by controller 12 via a signal provided to anelectric motor or actuator (not shown in FIG. 1) included with throttle62, a configuration that is commonly referred to as electronic throttlecontrol (ETC). Throttle position may be varied by the electric motor viaa shaft. Throttle 62 may control airflow from intake boost chamber 46 tointake manifold 44 and combustion chamber 30 (and other enginecylinders). The position of throttle plate 64 may be provided tocontroller 12 by throttle position signal TP from throttle positionsensor 158.

Exhaust gas sensor 126 is shown coupled to exhaust manifold 48 upstreamof emission control device 70. Sensor 126 may be any suitable sensor forproviding an indication of exhaust gas air/fuel ratio such as a linearoxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), atwo-state oxygen sensor or EGO, a HEGO (heated EGO), a NOx, HC, or COsensor. Emission control device 70 is shown arranged along exhaustpassage 58 downstream of exhaust gas sensor 126 and exhaust turbine 92.Device 70 may be a three way catalyst (TWC), NOx trap, various otheremission control devices, or combinations thereof.

An exhaust gas recirculation (EGR) system (not shown) may be used toroute a desired portion of exhaust gas from exhaust passage 58 to intakemanifold 44. Alternatively, a portion of combustion gases may beretained in the combustion chambers, as internal EGR, by controlling thetiming of exhaust and intake valves.

Controller 12 is shown in FIG. 1 as a conventional microcomputerincluding: microprocessor unit 102, input/output ports 104, read-onlymemory 106, random access memory 108, keep alive memory 110, and aconventional data bus. Controller 12 commands various actuators such asthrottle plate 64, wastegate 69, fuel injector 66, and the like.Controller 12 is shown receiving various signals from sensors coupled toengine 10, in addition to those signals previously discussed, including:engine coolant temperature (ECT) from temperature sensor 112 coupled tocooling sleeve 114; a position sensor 134 coupled to an acceleratorpedal 130 for sensing accelerator position adjusted by vehicle operator132; a measurement of engine manifold pressure (MAP) from pressuresensor 121 coupled to intake manifold 44; a measurement of boostpressure from pressure sensor 122 coupled to boost chamber 46; a profileignition pickup signal (PIP) from Hall effect sensor 118 (or other type)coupled to crankshaft 40; a measurement of air mass entering the enginefrom mass airflow sensor 120; and a measurement of throttle positionfrom sensor 158. Barometric pressure may also be sensed (sensor notshown) for processing by controller 12. In a preferred aspect of thepresent description, crankshaft sensor 118, which may be used as anengine speed sensor, may produce a predetermined number of equallyspaced pulses for every revolution of the crankshaft from which enginespeed (RPM) can be determined. Such pulses may be relayed to controller12 as a profile ignition pickup signal (PIP) as mentioned above.

As described above, FIG. 1 merely shows one cylinder of a multi-cylinderengine, and that each cylinder has its own set of intake/exhaust valves,fuel injectors, spark plugs, etc. Also, in the example embodimentsdescribed herein, the engine may be coupled to a starter motor (notshown) for starting the engine. The starter motor may be powered whenthe driver turns a key in the ignition switch on the steering column,for example. The starter is disengaged after engine start, for example,by engine 10 reaching a predetermined speed after a predetermined time.

During operation, each cylinder within engine 10 typically undergoes afour stroke cycle: the cycle includes the intake stroke, compressionstroke, expansion stroke, and exhaust stroke. During the intake stroke,generally, the exhaust valve 54 closes and intake valve 52 opens. Air isintroduced into cylinder 30 via intake manifold 44, and piston 36 movesto the bottom of the cylinder so as to increase the volume withincylinder 30. The position at which piston 36 is near the bottom of thecylinder and at the end of its stroke (e.g. when cylinder 30 is at itslargest volume) is typically referred to by those of skill in the art asbottom dead center (BDC). During the compression stroke, intake valve 52and exhaust valve 54 are closed. Piston 36 moves toward the cylinderhead so as to compress the air within cylinder 30. The point at whichpiston 36 is at the end of its stroke and closest to the cylinder head(e.g. when cylinder 30 is at its smallest volume) is typically referredto by those of skill in the art as top dead center (TDC). In a processhereinafter referred to as injection, fuel is introduced into thecombustion chamber. In a process hereinafter referred to as ignition,the injected fuel is ignited by known ignition devices such as sparkplug 91, resulting in combustion. Additionally or alternativelycompression may be used to ignite the air/fuel mixture. During theexpansion stroke, the expanding gases push piston 36 back to BDC.Crankshaft 40 converts piston movement into a rotational torque of therotary shaft. Finally, during the exhaust stroke, the exhaust valve 54opens to release the combusted air-fuel mixture to exhaust manifold 48and the piston returns to TDC. Note that the above is described merelyas an example, and that intake and exhaust valve opening and/or closingtimings may vary, such as to provide positive or negative valve overlap,late intake valve closing, early intake valve closing, or various otherexamples.

Turning now to FIG. 2, it shows a schematic diagram of multi-cylinderinternal combustion engine, which may be engine 10 of FIG. 1. Theembodiment shown in FIG. 2 includes a variable cam timing (VCT) system202, a cam profile switching (CPS) system 204, a turbocharger 290, andemission control device 70. It will be appreciated that engine systemcomponents introduced in FIG. 1 are numbered similarly and notreintroduced.

Engine 10 may include a plurality of combustion chambers (i.e.,cylinders) 212 which may be capped on the top by cylinder head 216. Inthe example shown in FIG. 2, engine 10 includes four combustionchambers: 31, 33, 35, and 37. It will be appreciated that the cylindersmay share a single engine block (not shown) and a crankcase (not shown).

As described earlier in reference to FIG. 1, each combustion chamber mayreceive intake air from intake manifold 44 via intake passage 42. Intakemanifold 44 may be coupled to the combustion chambers via intake ports.Each intake port may supply air and/or fuel to the cylinder it iscoupled to for combustion. Each intake port can selectively communicatewith the cylinder via one or more intake valves. Cylinders 31, 33, 35,and 37 are shown in FIG. 2 with two intake valves each. For example,cylinder 31 has two intake valves I1 and I2, cylinder 33 has two intakevalves I3 and I4, cylinder 35 has two intake valves I5 and I6, andcylinder 37 has two intake valves I7 and I8.

The four cylinders 31, 33, 35, and 37 are arranged in an inline-4configuration where cylinders 31 and 37 are positioned as outercylinders, and cylinders 33 and 35 are inner cylinders. In other words,cylinders 33 and 35 are arranged adjacent to each other and betweencylinders 31 and 37 on the engine block. Herein, outer cylinders 31 and37 may be described as flanking inner cylinders 33 and 35. While engine10 is depicted as an inline four engine with four cylinders, it will beappreciated that other embodiments may include a different number ofcylinders.

Each combustion chamber may exhaust combustion gases via one or moreexhaust valves into exhaust ports coupled thereto. Cylinders 31, 33, 35,and 37 are shown in FIG. 2 with two exhaust valves each for exhaustingcombustion gases. For example, cylinder 31 has two exhaust valves E1 andE2, cylinder 33 has two exhaust valves E3 and E4, cylinder 35 has twoexhaust valves E5 and E6, and cylinder 37 has two exhaust valves E7 andE8.

Each cylinder may be coupled to a respective exhaust port for exhaustingcombustion gases. In the example of FIG. 2, exhaust port 20 receivesexhaust gases from cylinder 31 via exhaust valves E1 and E2. Similarly,exhaust port 22 receives exhaust gases exiting cylinder 33 via exhaustvalves E3 and E4, exhaust port 24 receives exhaust gases from cylinder35 via exhaust valves E5 and E6, and exhaust port 26 receives exhaustgases leaving cylinder 37 via exhaust valves E7 and E8. Therefrom, theexhaust gases are directed via a split manifold system to exhaustturbine 92 of turbocharger 290. It will be noted that in the example ofFIG. 2, the split exhaust manifold is not integrated within the cylinderhead 216.

As shown in FIG. 2, exhaust port 20 may be fluidically coupled withfirst plenum 23 via runner 39 while exhaust port 22 may fluidicallycommunicate with first plenum 23 via runner 41. Further, exhaust port 24may be fluidically coupled to second plenum 25 via runner 43 whileexhaust port 26 may fluidically communicate with second plenum 25 viarunner 45. Thus, cylinders 31 and 33 may exhaust their combustion gasesinto first plenum 23 via respective exhaust ports 20 and 22, and viarunners 39 and 41 respectively. Runners 39 and 41 may combine atY-junction 250 into first plenum 23. Cylinders 35 and 37 may expel theirexhaust gases via exhaust ports 24 and 26, respectively, into secondplenum 25 via respective runners 43 and 45. Runners 43 and 45 maycombine at Y-junction 270 into second plenum 25. Thus, first plenum 23may not fluidically communicate with runners 43 and 45 from cylinders 24and 26 respectively. Further, second plenum 25 may not fluidicallycommunicate with runners 39 and 41 from cylinders 31 and 33,respectively. Additionally, first plenum 23 and second plenum 25 may notcommunicate with each other. In the depicted example, first plenum 23and second plenum 25 may not be included in the cylinder head 216 andmay be external to cylinder head 216.

Each combustion chamber may receive fuel from fuel injectors (not shown)coupled directly to the cylinder, as direct injectors, and/or frominjectors coupled to the intake manifold, as port injectors. Further,air charges within each cylinder may be ignited via spark fromrespective spark plugs (not shown). In other embodiments, the combustionchambers of engine 10 may be operated in a compression ignition mode,with or without an ignition spark.

As described earlier in reference to FIG. 1, engine 10 may include aturbocharger 290. Turbocharger 290 may include an exhaust turbine 92 andan intake compressor 94 coupled on a common shaft 96. The blades ofexhaust turbine 92 may be caused to rotate about the common shaft 96 asa portion of the exhaust gas stream discharged from engine 10 impingesupon the blades of the turbine. Intake compressor 94 may be coupled toexhaust turbine 92 such that compressor 94 may be actuated when theblades of exhaust turbine 92 are caused to rotate. When actuated,compressor 94 may then direct pressurized gas through boost chamber 46,and charge air cooler 90 to air intake manifold 44 from where it maythen be directed to engine 10. In this way, turbocharger 290 may beconfigured for providing a boosted air charge to the engine intake.

Intake passage 42 may include an air intake throttle 62 downstream ofcharge air cooler 90. The position of throttle 62 can be adjusted bycontrol system 15 via a throttle actuator (not shown) communicativelycoupled to controller 12. By modulating air intake throttle 62, whileoperating compressor 94, an amount of fresh air may be inducted from theatmosphere into engine 10, cooled by charge air cooler 90 and deliveredto the engine cylinders at compressor (or boosted) pressure via intakemanifold 44. To reduce compressor surge, at least a portion of the aircharge compressed by compressor 94 may be recirculated to the compressorinlet. A compressor recirculation passage 49 may be provided forrecirculating cooled compressed air from downstream of charge air cooler90 to the compressor inlet. Compressor recirculation valve 27 may beprovided for adjusting an amount of cooled recirculation flowrecirculated to the compressor inlet.

Turbocharger 290 may be configured as a multi-scroll turbochargerwherein the exhaust turbine 92 includes a plurality of scrolls. In thedepicted embodiment, exhaust turbine 92 includes two scrolls comprisinga first scroll 71 and a second scroll 73. Accordingly, turbocharger 290may be a twin scroll (or dual scroll) turbocharger with at least twoseparate exhaust gas entry paths flowing into, and through, exhaustturbine 92. The dual scroll turbocharger 290 may be configured toseparate exhaust gas from cylinders whose exhaust gas pulses interferewith each other when supplied to exhaust turbine 92. Thus, first scroll71 and second scroll 73 may be used to supply separate exhaust streamsto exhaust turbine 92.

In the example of FIG. 2, first scroll 71 is shown receiving exhaustfrom cylinders 31 and 33 via first plenum 23. Second scroll 73 isdepicted fluidly communicating with second plenum 25 and receivingexhaust from cylinders 35 and 37. Therefore, exhaust may be directedfrom a first outer cylinder (cylinder 31) and a first inner cylinder(cylinder 33) to a first scroll 71 of twin scroll turbocharger 290.Further, exhaust may be directed from a second outer cylinder (cylinder37) and a second inner cylinder (cylinder 35) to a second scroll 73 oftwin scroll turbocharger 290. The first scroll 71 may not receiveexhaust from second plenum 25 and second scroll 73 may not receiveexhaust pulses from first plenum 23.

Exhaust turbine 92 may include at least one wastegate to control anamount of boost provided by said exhaust turbine. As shown in FIG. 2, acommon wastegate 69 may be included in bypass passage 67 coupled betweenan inlet and outlet of the exhaust turbine 92 to control an amount ofexhaust gas bypassing exhaust turbine 92. Thus, a portion of exhaustgases flowing towards first scroll 71 from first plenum 23 may bediverted via passage 65 past wastegate 69 into bypass passage 67.Further, a different portion of exhaust gases flowing into second scroll73 from second plenum 25 may be diverted via passage 63 throughwastegate 69. Exhaust gases exiting turbine exhaust 92 and/or wastegate69 may pass through emission control device 70 and may exit the vehiclevia a tailpipe (not shown). In alternative dual scroll systems, eachscroll may include a corresponding wastegate to control the amount ofexhaust gas which passes through exhaust turbine 92.

Returning now to cylinders 31, 33, 35, and 37, as described earlier,each cylinder comprises two intake valves and two exhaust valves.Herein, each intake valve is actuatable between an open positionallowing intake air into a respective cylinder and a closed positionsubstantially blocking intake air from the respective cylinder. FIG. 2illustrates intake valves I1-I8 being actuated by a common intakecamshaft 218. Intake camshaft 218 includes a plurality of intake camsconfigured to control the opening and closing of the intake valves. Eachintake valve may be controlled by one or more intake cams, which will bedescribed further below. In some embodiments, one or more additionalintake cams may be included to control the intake valves. Further still,intake actuator systems may enable the control of intake valves.

Each exhaust valve is actuatable between an open position allowingexhaust gas out of a respective cylinder and a closed positionsubstantially retaining gas within the respective cylinder. FIG. 2 showsexhaust valves E1-E8 being actuated by a common exhaust camshaft 224.Exhaust camshaft 224 includes a plurality of exhaust cams configured tocontrol the opening and closing of the exhaust valves. Each exhaustvalve may be controlled by one or more exhaust cams, which will bedescribed further below. In some embodiments, one or more additionalexhaust cams may be included to control the exhaust valves. Further,exhaust actuator systems may enable the control of exhaust valves.

Intake valve actuator systems and exhaust valve actuator systems mayfurther include push rods, rocker arms, tappets, etc. Such devices andfeatures may control actuation of the intake valves and the exhaustvalves by converting rotational motion of the cams into translationalmotion of the valves. In other examples, the valves can be actuated viaadditional cam lobe profiles on the camshafts, where the cam lobeprofiles between the different valves may provide varying cam liftheight, cam duration, and/or cam timing. However, alternative camshaft(overhead and/or pushrod) arrangements could be used, if desired.Further, in some examples, cylinders 212 may each have only one exhaustvalve and/or intake valve, or more than two intake and/or exhaustvalves. In still other examples, exhaust valves and intake valves may beactuated by a common camshaft. However, in alternate embodiments, atleast one of the intake valves and/or exhaust valves may be actuated byits own independent camshaft or other device.

Engine 10 may be a variable displacement engine (VDE) and a subset ofthe four cylinders 212 may be deactivated, if desired, via one or moremechanisms. Therefore, controller 12 may be configured to deactivateintake and exhaust valves for selected cylinders when engine 10 isoperating in VDE mode. Intake and exhaust valves of selected cylindersmay be deactivated in the VDE mode via switching tappets, switchingrocker arms, or switching roller finger followers.

In the present example, cylinders 31, 35, and 37 are capable ofdeactivation. Each of these cylinders features a first intake cam and asecond intake cam per intake valve arranged on common intake camshaft218, and a first exhaust cam and a second exhaust cam per exhaust valvepositioned on common exhaust camshaft 224.

First intake cams have a first cam lobe profile for opening the intakevalves for a first intake duration. In the example of FIG. 2, firstintake cams C1 and C2 of cylinder 31, first intake cams C5, C6 ofcylinder 33, first intake cams C9, C10 of cylinder 35, and first intakecams C13, C14 of cylinder 37 may have a similar first cam lobe profilewhich opens respective intake valves for a similar duration and lift. Inother examples, first intake cams for different cylinders may havedifferent lobe profiles. Second intake cams are depicted as null camlobes which may have a profile to maintain their respective intakevalves in closed position. Thus, null cam lobes assist in deactivatingcorresponding valves in the VDE mode. In the example of FIG. 2, secondintake cams N1, N2 of cylinder 31, second intake cams N5, N6 of cylinder35, and second intake cams N9, N10 of cylinder 37 are null cam lobes.These null cam lobes can deactivate corresponding intake valves incylinders 31, 35, and 37.

Further, each of the intake valves may be actuated by a respectiveactuator system operatively coupled to controller 12. As shown in FIG.2, intake valves I1 and I2 of cylinder 31 may be actuated via actuatorsystem A2, intake valves I3 and I4 of cylinder 33 may be actuated viaactuator system A4, intake valves I5 and I6 of cylinder 35 may beactuated via actuator system A6, and intake valves I7 and I8 of cylinder37 may be actuated via actuator system A8.

Similar to the intake valves, each of the deactivatable cylinders (31,35, and 37) features a first exhaust cam and a second exhaust camarranged on common exhaust camshaft 224. First exhaust cams may have afirst cam lobe profile providing a first exhaust duration and lift. Inthe example of FIG. 2, first exhaust cams C3 and C4 of cylinder 31,first exhaust cams C7, C8 of cylinder 33, first exhaust cams C11, C12 ofcylinder 35, and first exhaust cams C15, C16 of cylinder 37 may have asimilar first cam lobe profile which opens respective exhaust valves fora given duration and lift. In other examples, first exhaust cams fordifferent cylinders may have different lobe profiles. Second exhaustcams are depicted as null cam lobes which may have a profile to maintaintheir respective exhaust valves in the closed position. Thus, null camlobes assist in deactivating exhaust valves in the VDE mode. In theexample of FIG. 2, second exhaust cams N3, N4 of cylinder 31, secondexhaust cams N7, N8 of cylinder 35, and second exhaust cams N11, N12 ofcylinder 37 are null cam lobes. These null cam lobes can deactivatecorresponding exhaust valves in cylinders 31, 35, and 37.

Further, each of the exhaust valves may be actuated by a respectiveactuator system operatively coupled to controller 12. Therefore, exhaustvalves E1 and E2 of cylinder 31 may be actuated via actuator system A1,exhaust valves E3 and E4 of cylinder 33 may be actuated via actuatorsystem A3, exhaust valves E5 and E6 of cylinder 35 may be actuated viaactuator system A5, and exhaust valves E7 and E8 of cylinder 37 may beactuated via actuator system A7.

Cylinder 33 (or first inner cylinder) may not be capable of deactivationand may not include null cam lobes for its intake and exhaust valves.Consequently, intake valves I3 and I4 of cylinder 33 may not bedeactivatable and are only operated by first intake cams C5 and C6respectively. Thus, intake valves I3 and I4 of cylinder 33 may not beoperated by null cam lobes. Likewise, exhaust valves E3 and E4 may notbe deactivatable and are only operated by first exhaust cams C7 and C8.Further, exhaust valves E3 and E4 may not be operated by null cam lobes.Therefore, each intake valve and each exhaust valve of cylinder 33 maybe actuated by a single respective cam.

It will be appreciated that other embodiments may include differentmechanisms known in the art for deactivating intake and exhaust valvesin cylinders. Such embodiments may not utilize null cam lobes fordeactivation. For example, hydraulic roller finger follower systems maynot use null cam lobes for cylinder deactivation.

Further, other embodiments may include reduced actuator systems. Forexample, a single actuator system may actuate intake valves I1 and I2 aswell as exhaust valves E1 and E2. This single actuator system wouldreplace actuator systems A1 and A2 providing one actuator system forcylinder 31. Other combinations of actuator systems are also possible.

CPS system 204 may be configured to translate specific portions ofintake camshaft 218 longitudinally, thereby causing operation of intakevalves I1-I8 to vary between respective first intake cams and secondintake cams (where applicable). Further, CPS system 204 may beconfigured to translate specific portions of exhaust camshaft 224longitudinally, thereby causing operation of exhaust valves E1-E8 tovary between respective first exhaust cams and second exhaust cams. Inthis way, CPS system 204 may switch between a first cam for opening avalve for a first duration, and a second cam, for opening the valve fora second duration. In the given example, CPS system 204 may switch camsfor intake valves in cylinders 31, 35, and 37 between a first cam foropening the intake valves for a first duration, and a second null camfor maintaining intake valves closed. Further, CPS system 204 may switchcams for exhaust valves in cylinders 31, 35, and 37 between a first camfor opening the exhaust valves for a first duration, and a second nullcam for maintaining exhaust valves closed. In the example of cylinder33, CPS system 204 may not switch cams for the intake and exhaust valvesas cylinder 33 is configured with one cam per valve, and may not bedeactivated.

CPS system 204 may receive signals from controller 12 to switch betweendifferent cam profiles for different cylinders in engine 10 based onengine operating conditions. For example, during low engine loads,engine operation may be in a two-cylinder mode. Herein, cylinders 35 and37 may be deactivated via the CPS system 204 actuating a switching ofcams from first intake and first exhaust cams to second, null intake andsecond, null exhaust cams for each valve. Simultaneously, cylinders 31and 33 may be maintained operative with their intake and exhaust valvesbeing actuated by their respective first cams.

In another example, at a medium engine load, engine 10 may be operatedin a three-cylinder mode. Herein, CPS system 204 may be configured toactuate the intake and exhaust valves of cylinders 33, 35, and 37 withtheir respective first intake cams. Concurrently, cylinder 31 may bedeactivated by CPS system 204 via actuating the intake and exhaustvalves of cylinder 31 with respective second, null cams.

Engine 10 may further include VCT system 202. VCT system 202 may be atwin independent variable camshaft timing system, for changing intakevalve timing and exhaust valve timing independently of each other. VCTsystem 202 includes intake camshaft phaser 230 and exhaust camshaftphaser 232 for changing valve timing. VCT system 202 may be configuredto advance or retard valve timing by advancing or retarding cam timing(an example engine operating parameter) and may be controlled viacontroller 12. VCT system 202 may be configured to vary the timing ofvalve opening and closing events by varying the relationship between thecrankshaft position and the camshaft position. For example, VCT system202 may be configured to rotate intake camshaft 218 and/or exhaustcamshaft 224 independently of the crankshaft to cause the valve timingto be advanced or retarded. In some embodiments, VCT system 202 may be acam torque actuated device configured to rapidly vary the cam timing. Insome embodiments, valve timing such as intake valve closing (IVC) andexhaust valve closing (EVC) may be varied by a continuously variablevalve lift (CVVL) device.

The valve/cam control devices and systems described above may behydraulically powered, or electrically actuated, or combinationsthereof.

Engine 10 may be controlled at least partially by a control system 15including controller 12 and by input from a vehicle operator via aninput device (FIG. 1). Control system 15 is shown receiving informationfrom a plurality of sensors 16 (various examples of which were describedin reference to FIG. 1) and sending control signals to a plurality ofactuators 81. As one example, control system 15, and controller 12, cansend control signals to and receive a cam timing and/or cam selectionmeasurement from CPS system 204 and VCT system 202. As another example,actuators 81 may include fuel injectors, wastegate 69, compressorrecirculation valve 27, and throttle 62. Controller 12 may receive inputdata from the various sensors, process the input data, and trigger theactuators in response to the processed input data based on instructionor code programmed therein corresponding to one or more routines.Additional system sensors and actuators will be elaborated below withreference to FIG. 5.

FIG. 4 depicts an alternate example embodiment of engine 10 with anasymmetric exhaust layout, unlike the symmetric exhaust layout of FIG.2. Specifically, the asymmetric layout comprises directing exhaust fromcylinder 31 (or the first outer cylinder) to first scroll 71 of exhaustturbine 92 and directing exhaust from cylinders 33, 35, and 37 (or thefirst inner cylinder, the second inner cylinder, and the second outercylinder) to second scroll 73 of exhaust turbine 92. In comparison, theembodiment of FIG. 2 depicts a symmetric exhaust layout wherein firstscroll 71 and second scroll 73 of exhaust turbine 92 each receiveexhaust from two cylinders. The symmetric exhaust layout may provideimproved turbine efficiency relative to the asymmetric exhaust layout.

In the example of FIG. 4, first scroll 71 of exhaust turbine 92 mayreceive exhaust only from cylinder 31 via exhaust port 20 and runner 39while second scroll 73 of exhaust turbine 92 may receive exhaust fromcylinders 33, 35, and 37 via respective ports 22, 24, and 26, andrespective runners 41, 43, and 45. Further, runners 41, 43, and 45 mayconverge into plenum 425 before delivering exhaust to exhaust turbine92. As depicted in FIG. 4, runners 43 and 45 may join plenum 425 atY-junction 470. Further, runner 41 may join plenum 425 at Y-junction450. Plenum 425 may direct combusted gases to a first pipe 461 whichdelivers exhaust to second scroll 73 of exhaust turbine 92. Duringconditions when lower boost is demanded, wastegate 69 may be opened toreceive a portion of exhaust gases from plenum 425 via passage 63.Likewise, a portion of exhaust may be diverted from runner 39 (and firstscroll 71) through passage 65 and past wastegate 69.

In the example of the asymmetric layout, second scroll 73 may be largerin size than first scroll 71. For example, second scroll 73 may bedesigned to receive a higher quantity of exhaust gases that may bereceived from three cylinders (33, 35, and 37).

Further details of the symmetric and asymmetric exhaust layouts of FIGS.2 and 4 will be elaborated in reference to FIGS. 6, 7, and 8. It will beappreciated that the exhaust layouts provided may allow a more compactarrangement within the engine between the turbocharger and the cylinderhead.

As mentioned earlier, engine 10 of FIGS. 1 and 2 may be operated in VDEmode or non-VDE (all cylinders firing) mode. In order to provide fueleconomy benefits along with reduced noise, vibration and harshness(NVH), example engine 10 may be primarily operated in either an evenfiring three-cylinder or an even firing two-cylinder VDE mode. A firstversion of a four-cylinder crankshaft wherein engine firing (or cylinderstrokes) occurs at 180 crank angle (CA) degree intervals may introduceNVH due to uneven firing when operating in a three-cylinder mode. Forexample, in a four-cylinder engine with the first version of thecrankshaft enabling a firing order of 1-3-4-2 may fire at the followinguneven intervals: 180°-180°-360° when operated in three-cylinder mode(1-3-4).

In order for engine 10 to operate in the three-cylinder mode withreduced NVH, a crankshaft that allows even firing during three-cylindermode operation may be desired. For example, a crankshaft may be designedto fire three cylinders at 240° intervals while a fourth cylinder isdeactivated. By providing a crankshaft that allows even firing in thethree-cylinder mode, engine 10 may be operated for longer periods in thethree-cylinder mode which can enhance fuel economy and ease NVH.

Accordingly, an example crankshaft 300 that may be utilized foroperating engine 10 in a two-cylinder or three-cylinder mode with evenfiring is shown in FIG. 3. FIG. 3 illustrates a perspective view ofcrankshaft 300. Crankshaft 300 may be crankshaft 40 shown in FIG. 1. Thecrankshaft depicted in FIG. 3 may be utilized in an engine, such asengine 10 of FIGS. 2 and 4, having an inline configuration in which thecylinders are aligned in a single row. A plurality of pistons 36 may becoupled to crankshaft 300, as shown. Further, since engine 10 is aninline four-cylinder engine, FIG. 3 depicts four pistons arranged in asingle row along a length of the crankshaft 300.

Crankshaft 300 has a crank nose end 330 (also termed front end) withcrank nose 334 for mounting pulleys and/or for installing a harmonicbalancer (not shown) to reduce torsional vibration. Crankshaft 300further includes a flange end 310 (also termed rear end) with a flange314 configured to attach to a flywheel (not shown). In this way, energygenerated via combustion may be transferred from the pistons to thecrankshaft and flywheel, and thereon to a transmission thereby providingmotive power to a vehicle.

Crankshaft 300 may also comprise a plurality of pins, journals, webs(also termed, cheeks), and counterweights. In the depicted example,crankshaft 300 includes a front main bearing journal 332 and a rear mainbearing journal 316. Apart from these main bearing journals at the twoends, crankshaft 300 further includes three main bearing journals 326positioned between front main bearing journal 332 and rear main bearingjournal 316. Thus, crankshaft 300 has five main bearing journals whereineach journal is aligned with a central axis of rotation 350. The mainbearing journals 316, 332, and 326 support bearings that are configuredto enable rotation of crankshaft 300 while providing support to thecrankshaft. In alternate embodiments, the crankshaft may have more orless than five main bearing journals.

Crankshaft 300 also includes a first crank pin 348, a second crank pin346, a third crank pin 344, and a fourth crank pin 342 (arranged fromcrank nose end 330 to flange end 310). Thus, crankshaft 300 has a totalof four crank pins. However, crankshafts having an alternate number ofcrank pins have been contemplated. Crank pins 342, 344, 346, and 348 mayeach be mechanically and pivotally coupled to respective pistonconnecting rods 312, and thereby, respective pistons 36. It will beappreciated that during engine operation, crankshaft 300 rotates aroundthe central axis of rotation 350. Crank webs 318 may support crank pins342, 344, 346, and 348. Crank webs 318 may further couple each of thecrank pins to the main bearing journals 316, 332, and 326. Further,crank webs 318 may be mechanically coupled to counterweights 320 todampen oscillations in the crankshaft 300. It may be noted that allcrank webs in crankshaft 300 may not be labeled in FIG. 3.

The second crank pin 346 and the first crank pin 348 are shown atsimilar positions relative to central axis of rotation 350. Toelaborate, pistons coupled to first crank pin 348 and second crank pin346 respectively may be at similar positions in their respectivestrokes. First crank pin 348 may also be aligned with second crank pin346 relative to central axis of rotation 350. Further, the second crankpin 346, the third crank pin 344 and the fourth crank pin 342 may bearranged 120 degrees apart from each other around the central axis ofrotation 350. For example, as depicted in FIG. 3 for crankshaft 300,third crank pin 344 is shown swaying towards the viewer, fourth crankpin 342 is moving away from the viewer (into the paper) while secondcrank pin 346 and first crank pin 348 are aligned with each other andare in the plane of the paper.

Inset 360 shows a schematic drawing of crankshaft 300 depicting thepositions of the four crank pins relative to each other and relative tocentral axis of rotation 350. Inset 370 shows a schematic diagram of aside view of crankshaft 300 as viewed from the rear end (or flange end310) of the crankshaft looking toward the front end (or crank nose end330) along the central axis of rotation 350. Inset 370 indicates therelative positions of the crank pins in relation to the center axis ofcrankshaft 300 and central axis of rotation 350.

As shown in inset 360, the fourth crank pin 342, and the third crank pin344 are depicted swaying in substantially opposite directions to eachother. To elaborate, when viewed from the end of rear main bearingjournal 316 towards front main bearing journal 332, third crank pin 344is angled towards the right while fourth crank pin 342 is angled towardsthe left, relative to the central axis of rotation 350. This angularplacement of third crank pin 344 relative to fourth crank pin 342 isalso depicted in inset 370.

Further, it will be observed that third crank pin 344 and fourth crankpin 342 may not be arranged directly opposite from each other. Thesecrank pins may be positioned 120 degrees apart in the clockwisedirection as measured specifically from third crank pin 344 towardsfourth crank pin 342 and as viewed from the flange (rear) end 310 withrear main bearing journal 316 towards crank nose end 330 with front mainbearing journal 332. The fourth crank pin 342 and the third crank pin344 are, therefore, angled relative to one another around the centralaxis of rotation 350. Similarly, the third crank pin 344 and the secondcrank pin 346 are angled relative to one another around the central axisof rotation 350. Further, first crank pin 348 and second crank pin 346are shown aligned and parallel with each other around the central axisof rotation 350. Additionally, first crank pin 348 and second crank pin346 are positioned adjacent to each other. As shown in inset 370, thesecond crank pin 346, the third crank pin 344 and the fourth crank pin342 are positioned 120 degrees apart from each other around the centeraxis of crankshaft 300. Further, first crank pin 348 and second crankpin 346 are positioned vertically above the central axis of rotation 350(e.g., at zero degrees) while third crank pin 344 is positioned 120degrees clockwise from first crank pin 348 and second crank pin 346.Fourth crank pin 342 is positioned 120 degrees counterclockwise fromfirst crank pin 348 and second crank pin 346.

It will be appreciated that even though first crank pin 348 is depictedaligned with second crank pin 346, and each of the two pistons coupledto first crank pin 348 and second crank pin 346 is depicted in FIG. 3 ata TDC position, the two respective pistons may be at the end ofdifferent strokes. For example, the piston coupled to first crank pin348 may be at the end of a compression stroke while the pistonassociated with second crank pin 346 may be at the end of the exhauststroke. Thus, the piston coupled to first crank pin 348 may be 360 crankangle degrees (CAD) apart from the piston coupled to second crank pin346 when considered with respect to a 720 CAD engine firing cycle.

The crank pin arrangement of FIG. 3 supports an engine firing order of3-2-4 in the three-cylinder mode. Herein, the firing order 3-2-4comprises firing a third cylinder with a piston coupled to third crankpin 344 followed by firing a second cylinder with a piston coupled tosecond crank pin 346, and then firing a fourth cylinder with a pistoncoupled to fourth crank pin 342. Herein, each combustion event isseparated by an interval of 240° of crank angle.

The crank pin arrangement may also mechanically constrain a firing orderof 1-3-2-4 when all cylinders are activated in a non-VDE mode. Herein,the firing order 1-3-2-4 may comprise firing a first cylinder with apiston coupled to the first crank pin 348 followed by firing the thirdcylinder with its piston coupled to the third crank pin 344 next. Thesecond cylinder with piston coupled to the second crank pin 346 may befired after the third cylinder followed by firing the fourth cylinderwith piston coupled to the fourth crank pin 342. In the example ofengine 10 with crankshaft 300, firing events in the four cylinders withfiring order 1-3-2-4 may occur at the following uneven intervals:120°-240°-240°-120°. Since first crank pin 348 is aligned with secondcrank pin 346, and their piston strokes occur 360 crank angle degreesapart, firing events in the first cylinder and the second cylinder alsooccur at 360° intervals from each other. Engine firing events will befurther described in reference to FIGS. 6, 7, and 8.

Turning now to FIG. 5, it portrays a schematic illustration of engine 10including the cylinders, camshafts and crankshaft described in FIGS.1-4. As such, components of engine system introduced in FIGS. 1-4 arenumbered similarly in FIG. 5. It will be appreciated that engine 10 isdepicted in a reverse view relative to the view depicted in FIGS. 2 and4. In other words, cylinder 31 in FIGS. 2 and 4 is shown at extreme leftwhile cylinder 31 in FIG. 5 is shown at extreme right. Likewise,cylinders 33, 35, and 37 are reversed.

Crankshaft 300 in engine 10 of FIG. 5 is driven by reciprocating motionof pistons 36 coupled to crankshaft 300 via connecting rods 312. Therotational motion of crankshaft 300 drives intake camshaft 218 and asingle balance shaft 574. Intake camshaft 218 may be coupled tocrankshaft 300 via a linkage 564 (e.g., timing chain, belt, etc.) whilebalance shaft 574 may be coupled to crankshaft 300 via a linkage andgear system 578. A position of intake camshaft 218 may be sensed byintake camshaft position sensor 572. A similar sensor may sense theposition of exhaust camshaft 224 (not shown).

Single balance shaft 574 may be a weighted shaft to offset vibrationsduring engine operation. In one example, balance shaft 574 may have arocking couple for balancing cylinders 33, 35, and 37 with a singleweight added for balancing cylinder 31. In addition, single balanceshaft 574 may rotate in a direction counter to the rotational directionof crankshaft 300. Further, single balance shaft 574 may rotate at thesame speed as crankshaft 300. A single balance shaft may be sufficientto offset vibrations arising from engine 10 since engine 10 may largelyoperate in a three-cylinder or two-cylinder even firing mode. Further,the engine may experience fewer transitions between VDE modes andnon-VDE modes. By using a single balance shaft, instead of twin balanceshafts spinning at twice the engine speed, lower frictional losses maybe achieved enabling a reduction in fuel consumption.

Engine 10 of FIG. 5 is depicted with four cylinders (as in FIGS. 2 and4) 31, 33, 35, and 37 arranged in a single row. As described earlier,the four cylinders have two intake valves and two exhaust valves. Intakecamshaft 218 includes two cams for each intake valve of cylinders 31,35, and 37: a first cam to open a respective intake valve for a givenduration and lift, and a second, null cam to enable deactivation of theintake valves in these cylinders. As mentioned in reference to FIG. 2,cylinder 33 is not capable of deactivation and includes one intake camper intake valve. Exhaust camshaft 224 is not shown in FIG. 5.

FIG. 5 depicts the four crank pins of crankshaft 300 coupled to theirrespective pistons. As shown in the depicted example, first crank pin348 is coupled to a piston in cylinder 31 (or first cylinder), secondcrank pin 346 is coupled a piston in cylinder 33 (or second cylinder),third crank pin 344 is coupled to a piston in cylinder 35 (or thirdcylinder), and fourth crank pin 342 is coupled to a piston in cylinder37 (or fourth cylinder). As elaborated earlier in reference to FIG. 3,first crank pin 348 is shown aligned with second crank pin 346, but theassociated pistons may be 360 crank angle degrees apart in respect totheir engine strokes. Correspondingly, cylinder 31 and cylinder 33 maybe 360 crank angle degrees apart in respect to the strokes occurringwithin these cylinders. As noted earlier, cylinder 31 may be at the endof its compression stroke when cylinder 33 may be at the end of itsexhaust stroke. Thus, in the embodiment described herein, cylinders 31and 33 may experience engine strokes that are 360 crank angle (CA)degrees apart. Additionally, as described earlier, second crank pin 346,third crank pin 344, and fourth crank pin 342 may be positionedapproximately 120 degrees apart along the crankshaft. Further, cylinders33, 35, and 37 may experience engine strokes that are 240 CA degreesapart.

Operation of engine 10, particularly, the firing order, will bedescribed now in reference to FIGS. 6-8 which depict ignition timingdiagrams for the four cylinders of engine 10. FIG. 6 illustrates enginefiring in a two-cylinder VDE mode for engine 10, FIG. 7 depicts enginefiring in a three-cylinder VDE mode for engine 10, and FIG. 8 representsengine firing in a non-VDE mode for engine 10 wherein all four cylindersare activated. It will be appreciated that cylinders 1, 2, 3, and 4 inFIGS. 6-8 correspond to cylinders 31, 33, 35, and 37 respectively, ofFIGS. 2, 4, and 5. For each diagram, cylinder number is shown on they-axis and engine strokes are depicted on the x-axis. Further, ignition,and the corresponding combustion event, within each cylinder isrepresented by a star symbol between compression and power strokeswithin the cylinder. Further, additional diagrams 604, 704, and 804,portray cylinder firing events in each active cylinder in each modearound a circle representing 720 degrees of crank rotation.

Referring to FIG. 6, an example engine firing diagram in two-cylinderVDE mode for engine 10 is illustrated. Herein, cylinders 3 and 4 aredeactivated by actuating the intake and exhaust valves of thesecylinders via their respective null cams. Cylinders 1 and 2 may be fired360 CA degrees apart in a firing order of 1-2-1-2. As shown in FIG. 6,cylinder 1 may commence a compression stroke at the same time thatcylinder 2 begins an exhaust stroke. As such, each engine stroke incylinders 1 and 2 is spaced 360 CA degrees apart. For example, anexhaust stroke in cylinder 2 may occur 360 CA degrees after an exhauststroke in cylinder 1. Similarly, ignition events in the engine arespaced 360 CA degrees apart and accordingly, power strokes in the twoactive cylinders occur 360 CA degrees apart from each other. Thetwo-cylinder VDE mode may be utilized during low engine load conditionswhen torque demand is lower. By operating in the two-cylinder mode, fueleconomy benefits may also be attained.

Turning now to FIG. 7, it portrays an example cylinder firing diagramfor the cylinder firing order in an example three-cylinder VDE mode forengine 10 wherein three cylinders are activated. In this example,cylinder 1 may be deactivated while cylinders 2, 3, and 4 are activated.Ignition and combustion events within the engine and between the threeactivated cylinders may occur at 240 CA degree intervals similar to athree-cylinder engine. Herein, firing events may occur at evenly spacedintervals. Likewise, each engine stroke within the three cylinders mayoccur at 240 CA degree intervals. For example, an exhaust stroke incylinder 2 may be followed by an exhaust stroke in cylinder 4 at about240 CA degrees after the exhaust stroke in cylinder 2. Similarly, theexhaust stroke in cylinder 4 may followed by an exhaust stroke incylinder 3 after an interval of 240 CA degrees. Firing events in theengine may occur similarly. An example firing order for thethree-cylinder VDE mode may be 2-4-3-2-4-3. As illustrated at 704,cylinder 3 may be fired approximately 240 CA degrees after cylinder 4 isfired, cylinder 2 may be fired approximately 240 CA degrees after thefiring event in cylinder 3, and cylinder 4 may be fired approximately240 CA degrees after the firing event in cylinder 2. Thus, a method ofoperating an engine may comprise, during a first VDE mode in an enginehaving four cylinders, deactivating a first cylinder of the fourcylinders and firing a second, third, and fourth cylinder of the fourcylinders, each firing event separated by 240 degrees of crank angle(CA).

It will be appreciated that the even firing intervals of 240 CA degreesin the three-cylinder VDE mode may be approximate. In one example, thefiring interval between cylinder 3 and cylinder 2 may be 230 CA degrees.In another example, the firing interval between cylinder 3 and cylinder2 may be 255 CA degrees. In yet another example, the firing intervalbetween cylinder 3 and cylinder 2 may be exactly 240 CA degrees.Likewise, the firing interval between cylinder 2 and cylinder 4 may varyin a range between 230 CA degrees and 255 CA degrees. The same variationmay apply to firing intervals between cylinder 4 and cylinder 3. Othervariations may also be possible.

Referring to FIG. 2 (or FIG. 4), it may be appreciated that the firingorder of 2-4-3 may enable improved balance and reduced NVH. For example,cylinder 2 represents cylinder 33 of FIGS. 2 and 4 and is positioned asa first inner cylinder, cylinder 4 represents cylinder 37 of FIGS. 2 and4 and is positioned as a second outer cylinder, and cylinder 3represents cylinder 35 of FIGS. 2 and 4 and is positioned as a secondinner cylinder. Based on the positions of activated cylinders within theengine block, the firing order of 2-4-3 may provide better balance andmay reduce noise and vibrations.

Further, the three-cylinder VDE mode may be selected for engineoperation during engine idling conditions. Noise and vibration may bemore prominent during engine idle conditions and the even firingthree-cylinder mode with stable firing may be a more suitable option forengine operation during these conditions.

Turning now to FIG. 8, it portrays an example cylinder firing diagramfor the cylinder firing order in an example non-VDE mode for engine 10wherein all four cylinders are activated. In the non-VDE mode, engine 10may be fired unevenly based on the design of crankshaft 300. In oneexample, crankshaft 300 shown in FIG. 3 may produce the cylinder firingorder shown in FIG. 8. As shown in the depicted example, cylinder 1 maybe fired between cylinders 3 and 4. In one example, cylinder 1 may befired approximately 120 crank angle (CA) degrees after cylinder 4 isfired. In one example, cylinder 1 may be fired exactly 120 CA degreesafter cylinder 4 is fired. In another example, cylinder 1 may be fired115 CA degrees after cylinder 4 fires. In yet another example, cylinder1 may be fired 125 CA degrees after firing cylinder 4. Further, cylinder1 may be fired approximately 120 CA degrees before cylinder 3 is fired.For example, cylinder 1 may be fired in a range of between 115 and 125CA degrees before cylinder 3 is fired. In addition, cylinders 2, 3, and4 may continue to have combustion events 240 CA degrees apart with acombustion event in cylinder 1 occurring approximately midway betweenthe combustion events in cylinder 4 and cylinder 3. Therefore, engine 10may be fired with the following firing order: 1-3-2-4 (or 2-4-1-3 or3-2-4-1 or 4-1-3-2 since the firing is cyclic) at uneven intervalswherein cylinder 1 is the uneven firing cylinder. As illustrated at 804,cylinder 3 may be fired approximately 120 degrees of crank rotationafter cylinder 1 is fired, cylinder 2 may be fired approximately 240degrees of crank rotation after firing cylinder 3, cylinder 4 may befired at approximately 240 degrees of crank rotation after firingcylinder 2, and cylinder 1 may be fired again at approximately 120degrees of crank rotation after firing cylinder 4. In other examples,the intervals between the firing events in the four cylinders may varyfrom the intervals mentioned above.

Accordingly, during the non-VDE mode in the example four-cylinder engine10, a method of engine operation may comprise firing three cylinderswith a middle cylinder firing a first number of crankshaft degreesbetween an earlier cylinder and a later cylinder, and firing a fourthcylinder between the later cylinder and the earlier cylinder at doublethe first number of crankshaft degrees therebetween. To elaborate inreference to FIG. 8, the method includes firing three cylinders, such ascylinders 4, 1, and 3, wherein the middle cylinder may be cylinder 1firing a first number of crankshaft degrees, e.g., 120°, between theearlier cylinder, cylinder 4, and the later cylinder, cylinder 3. Thefourth cylinder in this example, cylinder 2 may be fired at double thefirst number of crankshaft degrees, e.g., 240°, between the latercylinder, cylinder 3, and the earlier cylinder, cylinder 4. Engine 10may have a firing sequence of: 1-3-2-4-1-3-2-4 such that the firingorder may be the earlier cylinder, middle cylinder and later cylinder(e.g. cylinders 4, 1, and 3 respectively) while the fourth cylinder,cylinder 2, is fired away from the three cylinders and not between thethree cylinders 4, 1, and 3. For example, the fourth cylinder may fireafter the later cylinder. Further, the four cylinders may bemechanically constrained to fire in the order identified above. Inanother example, no other cylinders may fire at any other timings inbetween.

Additionally, during a given condition, which may be medium engine load,the middle cylinder (cylinder 1) may be deactivated and the earliercylinder, the later cylinder and the fourth cylinder may be fired atevenly spaced intervals of about 240 crankshaft degrees. The firingorder herein may be as follows: the earlier cylinder, the latercylinder, and the fourth cylinder.

In other words, a four-cylinder engine may include a crankshaftconfigured to fire three of the four cylinders at 240 crank angle degreeintervals and fire the remaining cylinder of the four cylinders midwaybetween two of the three cylinders being fired 240 crank angle degreesapart. An example firing sequence may include firing a first cylinder,firing a second cylinder at about 120 crank angle degrees after firingthe first cylinder, firing a third cylinder at about 240 crank angledegrees after firing the second cylinder, and firing a fourth cylinderat about 240 crank angle degrees after firing the third cylinder, andfiring the first cylinder at about 120 crank angle degrees after firingthe fourth cylinder. Thus, the first cylinder may be fired at about 120crank angle degrees between the fourth cylinder and the second cylinderand the third cylinder may be fired at 240 crank angle degrees (ordouble of 120 crank angle degrees) between the fourth and secondcylinders. The engine may also be operated in a three-cylinder modewherein the first cylinder is deactivated, and the second, third andfourth cylinders are fired at about 240 crank angle degree intervalsfrom each other. Additionally, the engine may be operated in atwo-cylinder mode by deactivating two cylinders and firing the remainingtwo cylinders 360 crank angle degrees apart from each other.

Referring back to FIGS. 2 and 4, the symmetric and asymmetric exhaustlayouts will now be described further. As elaborated earlier, thesymmetric exhaust layout of FIG. 2 depicts first scroll 71 of exhaustturbine 92 receiving exhaust from cylinders 31 and 33, while secondscroll 73 of exhaust turbine 92 receives exhaust from cylinders 35 and37. An alternate embodiment may feature an asymmetric exhaust layout,such as that shown in FIG. 4, wherein cylinder 31 exhausts directly tofirst scroll 71 while cylinders 33, 35, and 37 expel their combustiongases to second scroll 73. By exhausting directly, cylinder 31 may onlyexhaust its combustion products to first scroll 71 and not to secondscroll 73.

In a first version four-cylinder engine including a divided exhaustmanifold featuring a twin scroll turbocharger, exhaust runners fromcylinders 1 and 4 (first and second outer cylinders or cylinders 31 and37) may combine to deliver their exhaust to a first scroll of theexhaust turbine while cylinders 2 and 3 (first and second innercylinders or cylinders 33 and 35) may deliver their exhaust to a secondscroll of the exhaust turbine. This exhaust layout may be suitable for afour cylinder engine with a firing sequence of 1-3-4-2 so that anexhaust gas pressure pulse from cylinder 1 may not interfere with theability of cylinder 2 to expel its exhaust gases.

However, in a second version, such as the example embodiment offour-cylinder engine 10 shown in FIGS. 2, 4, 5 which has a firingsequence of 1-3-2-4 (e.g., cylinder 31 followed by cylinder 35 followedby cylinder 33 followed by cylinder 37), the exhaust layout describedfor the first version may not be suitable and may degrade turbineefficiency. For example, if the example engine 10 shown in FIGS. 2, 4,and 5 has an exhaust layout such as that of the first version, anexhaust gas pressure pulse from cylinder 31 (first outer cylinder) mayinterfere with the ability of cylinder 37 (second outer cylinder) toexpel its exhaust gases. As will be observed in FIG. 8, cylinder 31 (orcylinder 1) may be ending its expansion stroke and opening its exhaustvalves while cylinder 37 (or cylinder 4) still has its exhaust valvesopen. Therefore, in order to separate exhaust pulses and increase pulseenergy driving the turbine, the second version may include exhaustrunners from cylinders 1 and 2 (or cylinders 31 and 33) merging intofirst plenum 23, and exhaust runners from cylinders 3 and 4 (orcylinders 35 and 37, respectively) combining into second plenum 25.

It will be appreciated that in the symmetric layout, first scroll 71receives exhaust pulses from cylinders 31 and 33 that are separated byat least 360 CA degrees while second scroll 73 receives exhaust pulsesfrom cylinders 35 and 37 that are at least 240 CA degrees apart. In thisway, each scroll may receive an exhaust pulse that is separated from thenext pulse by at least 240 CA degrees.

Therefore, a method for operating engine 10 in a non-VDE mode maycomprise directing exhaust from a first outer cylinder (cylinder 31) anda first inner cylinder (cylinder 33) of four cylinders to a first scroll71 of a twin scroll turbocharger 290, directing exhaust from a secondouter cylinder (cylinder 37) and a second inner cylinder (cylinder 35)of the four cylinders to a second scroll 73 of the twin scrollturbocharger 290, and firing all cylinders in an uneven mode, e.g., withat least one uneven firing. The method may include firing all cylindersin an uneven mode as follows: firing the second inner cylinder at 120degrees of crank rotation after the first outer cylinder is fired,firing the first inner cylinder 240 crank angle degrees after firing thesecond inner cylinder, firing the second outer cylinder 240 crank angledegrees after firing the first inner cylinder, and firing the firstouter cylinder 120 crank angle degrees after firing the second outercylinder. Thus, firing events in the first outer cylinder and the firstinner cylinder may be separated by at least 360 crank angle degreeswhile firing events in the second outer cylinder and the second innercylinder may be separated by at least 240 crank angle degrees.

A first VDE mode may include operating engine 10 in a three-cylindermode. A method for operating engine 10 in three-cylinder mode maycomprise deactivating the first outer cylinder (cylinder 31) anddirecting exhaust only from first inner cylinder (cylinder 33) to thefirst scroll 71 of the twin scroll turbocharger. The second scroll 73may continue to receive exhaust from second outer and second innercylinders. The first VDE mode may be used during a first condition thatmay include engine idling conditions (for reduced NVH). The first VDEmode may also be utilized during medium engine load conditions.

A second VDE mode may include operating engine 10 in a two-cylindermode. A method for operating engine 10 in two-cylinder mode may comprisedeactivating the second outer cylinder (cylinder 37) and the secondinner cylinder (cylinder 33). Thus, the engine may be operated byactivating the first outer cylinder (cylinder 31) and first innercylinder (cylinder 33). The second VDE mode may be used during lowengine load conditions.

In the example of the asymmetric exhaust layout, as shown in FIG. 4,first scroll 71 of exhaust turbine 92 may receive exhaust gasesapproximately every 720 CA degrees while second scroll 73 of exhaustturbine 92 may receive exhaust pulses approximately every 240 CAdegrees. In this layout as well, each scroll may receive an exhaustpulse that is separated from the next pulse by at least 240 CA degrees.In the three-cylinder mode, first scroll 71 may not receive exhaustpulses as cylinder 31 may be deactivated. However, second scroll 73 maycontinue to receive expelled exhaust from the three activated cylinders(cylinders 33, 35, and 37).

In the two-cylinder mode, cylinders 35 and 37 may be deactivated.Herein, first scroll 71 may receive exhaust pulses from cylinder 31approximately every 720 CA degrees while second scroll 73 may receiveexhaust pulses from cylinder 33 approximately every 720 CA degrees.Accordingly, exhaust turbine 92 may receive exhaust pulses approximatelyevery 360 CA degrees.

Scroll 73 is depicted in FIGS. 2, 4, 12, 13, and 14 of the presentdisclosure as an inboard scroll that is located closer to a centerhousing of the turbocharger 290. Further, scroll 71 in the above figuresis illustrated farther from the center housing of turbocharger 290. Itwill be appreciated that in other examples, the positions of scrolls 73and 71 may be swapped without departing from the scope of the presentdisclosure.

Therefore, a method of operating an engine in non-VDE mode with anasymmetric exhaust layout may comprise flowing exhaust from a firstouter cylinder (cylinder 31) of four cylinders to a first scroll 71 of atwin scroll turbocharger 290, flowing exhaust from a first innercylinder (cylinder 33), a second outer cylinder (cylinder 37) and asecond inner cylinder (cylinder 35) of the four cylinders to a secondscroll 73 of the twin scroll turbocharger 290, and during a firstcondition, operating all cylinders with at least one uneven firing. Thefirst condition may include high engine load conditions. The unevenfiring may include a similar firing interval to that described above fora symmetric exhaust layout wherein each of the first inner cylinder, thesecond outer cylinder and the second inner cylinder may be fired at 240crank angle degree intervals and the first outer cylinder may be firedapproximately midway between the firing of the second outer cylinder andthe second inner cylinder. Further, the first outer cylinder may befired at approximately 120 crank angle degrees after firing the secondouter cylinder and approximately 120 crank angle degrees before firingthe second inner cylinder. Herein, the first outer cylinder may be theone cylinder with uneven firing.

During a second condition, the engine may be operated in three-cylindermode by deactivating the first outer cylinder and firing the remainingthree cylinders at even intervals. For example, the remaining threecylinders may be operated with even firing with respect to each other.Herein, the first inner cylinder, the second outer cylinder, and thesecond inner cylinder may be fired at 240 crank angle degree intervalsbetween each cylinder. The second condition for using three-cylindermode may be under medium engine load conditions. In another example, thethree-cylinder mode may be used during idling conditions.

During a third condition, the engine may be operated in a two-cylindermode by deactivating the second outer and second inner cylinders.Herein, the remaining cylinders, first outer cylinder and first innercylinder, may be fired at even intervals of 360 crank angle degrees. Thethird condition for using the two-cylinder VDE mode may be during lowengine load conditions.

It will be appreciated that the two-cylinder VDE mode, three-cylinderVDE mode and non-VDE modes may also be used in a naturally aspiratedengine. In this example, a turbocharger may not be used.

Turning now to FIG. 9, it shows an example routine 900 for determining amode of engine operation in a vehicle based on engine load.Specifically, a two-cylinder VDE mode, a three-cylinder VDE mode, or anon-VDE mode of operation may be selected based on engine loads.Further, transitions between these modes of operation may be determinedbased on changes in engine loads. Routine 900 may be controlled by acontroller such as controller 12 of engine 10.

At 902, the routine includes estimating and/or measuring engineoperating conditions. These conditions may include, for example, enginespeed, engine load, desired torque (for example, from a pedal-positionsensor), manifold pressure (MAP), mass air flow (MAF), boost pressure,engine temperature, spark timing, intake manifold temperature, knocklimits, etc. At 904, the routine includes determining a mode of engineoperation based on the estimated engine operating conditions. Forexample, engine load may be a significant factor to determine enginemode of operation which includes two-cylinder VDE mode, three-cylinderVDE mode or non-VDE mode (also termed full-cylinder mode). In anotherexample, desired torque may also determine engine operating mode. Ahigher demand for torque may include operating the engine in non-VDE orfour-cylinder mode. A lower demand for torque may enable a transition ofengine operation to a VDE mode. As will be elaborated later in referenceto FIG. 11, in particular Map 1140, a combination of engine speed andengine load conditions may determine engine mode of operation.

At 906, therefore, routine 900 may determine if high (or very high)engine load conditions exist. For example, the engine may beexperiencing higher loads as the vehicle ascends a steep incline. Inanother example, an air-conditioning system may be activated therebyincreasing load on the engine. If it is determined that high engine loadconditions exist, routine 900 continues to 908 to activate all cylindersand operate in the non-VDE mode. In the example of engine 10 of FIGS. 2,4, and 5, all four cylinders may be operated during the non-VDE mode. Assuch, a non-VDE mode may be selected during very high engine loadsand/or very high engine speeds.

Further, at 910, the four cylinders may be fired in the followingsequence: 1-3-2-4 with cylinders 2, 3, and 4 firing about 240 CA degreesapart, and cylinder 1 firing about halfway between cylinder 4 andcylinder 3. As described earlier, when all cylinders are activated, afirst cylinder (cylinder 3) may be fired at 120 degrees of crankrotation after cylinder 1, a second cylinder (cylinder 2) may be firedat 240 degrees of crank rotation after firing the first cylinder, athird cylinder (cylinder 4) may be fired at 240 degrees of crankrotation after firing the second cylinder, and a fourth cylinder(cylinder 1) may be fired at 120 degrees of crank rotation after firingthe third cylinder. Routine 900 may then proceed to 926.

If at 906, it is determined that high engine load conditions do notexist, routine 900 progresses to 912 where it may determine if lowengine load conditions are present. For example, the engine may beoperating at a light load when cruising on a highway. In anotherexample, lower engine loads may occur when the vehicle is descending anincline. If low engine load conditions are determined at 912, routine900 continues to 916 to operate the engine in a two-cylinder VDE mode.Additionally, at 918, the two activated cylinders (cylinders 1 and 2)may be fired at 360 crank angle degree intervals. Routine 900 may thenproceed to 926.

If it is determined that low engine load conditions are not present,routine 900 progresses to 920 where it may determine medium engine loadoperation. Next, at 922, the engine may be operated in a three-cylinderVDE mode wherein cylinder 1 may be deactivated and cylinders 2, 3, and 4may be activated. Further, at 924, the three activated cylinders may befired 240 crank angle degrees apart such that the engine experiencescombustion events at 240 crank angle degree intervals.

Once an engine operating mode is selected and engine operation inselected mode is commenced (e.g., at one of 910, 916 or 924), routine900 may determine at 926 if a change in engine load is occurring. Forexample, the vehicle may complete ascending the incline to reach a morelevel road thereby reducing the existing high engine load to a moderateload (or low load). In another example, the air-conditioning system maybe deactivated. In yet another example, the vehicle may accelerate onthe highway to pass other vehicles so that engine load may increase froma light load to a moderate or high load. If it is determined at 926 thata change in load is not occurring, routine 900 continues to 928 tomaintain engine operation in the selected mode. Else, engine operationmay be transitioned at 930 to a different mode based on the change inengine load. Mode transitions will be described in detail in referenceto FIG. 10 which shows an example routine 1000 for transitioning from anexisting engine operation mode to a different operation mode based ondetermined engine loads.

At 932, various engine parameters may be adjusted to enable a smoothtransition and reduce torque disturbance during transitions. Forexample, it may be desired to maintain a driver-demanded torque at aconstant level before, during, and after the transition between VDEoperating modes. As such, when cylinders are reactivated, the desiredair charge and thus the manifold pressure (MAP) for the reactivatedcylinders may decrease (since a larger number of cylinders will now beoperating) to maintain constant engine torque output. To attain thedesired lower air charge, the throttle opening may be gradually reducedduring the preparing for transition. At the time of the actualtransition, that is, at the time of cylinder reactivation, the throttleopening may be substantially reduced to attain the desired airflow. Thisallows the air charge to be reduced during the transition withoutcausing a sudden drop in engine torque, while allowing the air chargeand MAP levels to be immediately reduced to the desired level at theonset of cylinder reactivation. Additionally or alternatively, sparktiming may be retarded to maintain a constant torque on all thecylinders, thereby reducing cylinder torque disturbances. Whensufficient MAP is reestablished, spark timing may be restored andthrottle position may be readjusted. In addition to throttle and sparktiming adjustments, valve timing may also be adjusted to compensate fortorque disturbances. Routine 900 may end after 932.

It should be noted that when the relative speed (or loads or other suchparameters) is indicated as being high or low, the indication refers tothe relative speed compared to the range of available speeds (or loadsor other such parameters, respectively). Thus, low engine loads orspeeds may be lower relative to medium and higher engine loads andspeeds, respectively. High engine loads and speeds may be higherrelative to medium (or moderate) and lower engine loads and speedsrespectively. Medium or moderate engine loads and speeds may be lowerrelative to high or very high engine loads and speeds, respectively.Further, medium or moderate engine loads and speeds may be greaterrelative to low engine loads and speeds, respectively.

Turning now to FIG. 11, it shows example maps 1120, 1140, and 1160featuring engine load-engine speed plots. Specifically, the mapsindicate different engine operation modes that are available atdifferent combinations of engine speeds and engine loads. Each of themaps shows engine speed plotted along the x-axis and engine load plottedalong the y-axis. Line 1122 represents a highest load that a givenengine can operate under at a given speed. Zone 1124 indicates afour-cylinder non-VDE mode for a four-cylinder engine, such as engine 10described earlier. Zone 1148 indicates a three-cylinder VDE mode withstandard intake durations and zone 1126 indicates a two-cylinder VDEmode for the four-cylinder engine.

Map 1120 depicts an example of a first version of a four-cylinderengine, wherein the lone available VDE mode is a two-cylinder mode VDEoption (unlike the embodiments in the present disclosure). Thetwo-cylinder mode (zone 1126) may be primarily used during low engineloads and moderate engine speeds. At all other engine speed-engine loadcombinations, a non-VDE mode may be used (zone 1124). As will beobserved in map 1120, zone 1126 occupies a smaller portion of the areaunder line 1122 relative to the area representing a non-VDE mode (zone1124). Therefore, an engine operating with two available modes (VDE andnon-VDE) may provide relatively minor improvements in fuel economy overan engine without variable displacement. Further, since the transitionbetween the two modes involves activation or deactivation of two out offour cylinders, more intrusive controls (e.g., larger changes to sparktiming along with adjustments to throttle and valve timings) may beneeded to compensate for torque disturbances during these transitions.As mentioned earlier, the first version of the four cylinder engine maynot provide an option of operating in three-cylinder mode due toincreased NVH issues.

Map 1140 depicts an example of engine operation for one embodiment ofthe present disclosure, e.g. engine 10 of FIGS. 2, 4, and 5. Herein, theengine may operate in one of two available VDE modes increasing fueleconomy benefits over the first version option described in reference toMap 1120. The engine may operate in two-cylinder VDE mode, as in theexample of Map 1120, during low engine loads at moderate engine speeds.Further, the engine may operate in three-cylinder VDE mode during lowload-low speed conditions, during moderate load-moderate speedconditions, and during moderate load-high speed conditions. At very highspeed conditions at all loads and at very high load conditions at allengine speeds, a non-VDE mode of operation may be utilized.

It will be appreciated from Map 1140 that the example engine of FIGS. 2,4, and 5 may operate substantially in a three-cylinder or a two-cylindermode. A non-VDE mode may be selected only during the high load and veryhigh engine speed conditions. Therefore, a relatively higher improvedfuel economy may be achieved. As described earlier, the engine may beoperated in three-cylinder and two-cylinder modes with even firingallowing reduced NVH issues. When operating in non-VDE mode, an unevenfiring pattern may be utilized which may produce a distinct exhaustnote.

It will be further appreciated that in the embodiment of engine 10 ofFIGS. 2, 4, and 5, a larger proportion of operating mode transitions mayinclude transitions from two-cylinder VDE mode to three-cylinder VDEmode or transitions from three-cylinder VDE mode to non-VDE mode.Further, fewer transitions involving a transition from four-cylindernon-VDE mode to two-cylinder VDE mode (and vice versa) may occur.Consequently, a smoother and easier transition in engine control may beenabled in the example embodiment of engine 10 described in reference toFIGS. 2, 4, and 5. Overall, drivability may be enhanced due to reducedNVH and smoother engine control.

An alternate engine operation for the example engine (e.g. engine 10 ofFIGS. 2, 4, and 5) is illustrated in Map 1160. Herein, the option of thetwo-cylinder VDE mode is unavailable and the engine may largely operatein an even firing three-cylinder VDE mode. For example, thethree-cylinder VDE mode may be operational during low load conditions atlow, moderate, and high speeds, and during moderate load conditions atlow, moderate, and high speeds. A transition to non-VDE mode may be madeonly under conditions including very high engine speeds, high loads, orvery high engine loads. In the example shown in Map 1160, transitionsbetween non-VDE and VDE modes may be significantly reduced, easing NVHand enabling smoother engine control. Further, in the example of engine10, solely one cylinder may include a deactivation mechanism providing adecrease in costs. The fuel economy benefits may be relativelydiminished in comparison to the engine operation example of Map 1140.

Map 1180 of FIG. 11 depicts an engine operation example for an alternateengine embodiment which will be described further in reference to FIGS.14, 15, and 16.

Turning now to FIG. 10, routine 1000 for determining transitions inengine operating modes based on engine load and engine speed conditionsis described. Specifically, the engine may be transitioned from anon-VDE mode to one of two VDE modes and vice versa, and may also betransitioned between the two VDE modes.

At 1002, the current operating mode may be determined. For example, thefour-cylinder engine may be operating in a non-VDE full cylinder mode, athree-cylinder VDE mode, or a two-cylinder VDE mode. At 1004, it may bedetermined if the engine is operating in the four-cylinder mode. If not,routine 1000 may move to 1006 to determine if the current mode of engineoperation is the three-cylinder VDE mode. If not, routine 1000 maydetermine at 1008 if the engine is operating in the two-cylinder VDEmode. If not, routine 1000 returns to 1004.

At 1004, if it is confirmed that a non-VDE mode of engine operation ispresent, routine 1000 may continue to 1010 to confirm if engine loadand/or engine speed have decreased. If the existing engine operatingmode is a non-VDE mode with all four cylinders activated, the engine maybe experiencing high or very high engine loads. In another example, anon-VDE mode of engine operation may be in response to very high enginespeeds. Thus, if the engine is experiencing high engine loads to operatein a non-VDE mode, a change in operating mode may occur with a decreasein load. A decrease in engine speed may also enable a transition to aVDE mode. An increase in engine load or speed may not change operatingmode.

If it is confirmed that a decrease in load and/or speed has notoccurred, at 1012, the existing engine operating mode may be maintainedand routine 1000 ends. However, if it is determined that a decrease inengine load and/or speed has occurred, routine 1000 progresses to 1014to determine if the decrease in engine load and/or speed makes itsuitable to operate in three-cylinder mode. As described earlier inreference to Map 1140 of FIG. 11, a transition to moderate load-moderatespeed conditions, and to moderate load-high speed conditions may enableengine operation in three-cylinder VDE mode. It will be appreciated thata transition to three-cylinder VDE mode may also occur during lowspeed-low load conditions, as shown in Map 1140 of FIG. 11. Accordingly,if it is confirmed that existing load and/or speed conditions enable atransition to three-cylinder mode, at 1016, a transition tothree-cylinder VDE mode may occur. Further, cylinder 1 of the fourcylinders may be deactivated while maintaining the remaining threecylinders activated. Further still, the remaining three cylinders maycontinue to be fired about 240 CA degrees apart from each other. Routine1000 may then end.

If at 1014 it is determined that the decrease in engine load and/orengine speed is not suitable for operating in three-cylinder mode,routine 1000 continues to 1018 to confirm that the decrease in engineload and/or engine speed enables engine operation in two-cylinder mode.As depicted in Map 1140 of FIG. 11, low engine loads with moderateengine speeds may enable a two-cylinder VDE mode. If the engine loadand/or engine speed are not suited for the two-cylinder mode, routine1000 returns to 1010. Else, at 1020 a transition to two-cylinder VDEmode from non-VDE mode may be completed by deactivating cylinders 3 and4, while maintaining cylinders 1 and 2 in an activated condition.Cylinders 1 and 2 may be fired at 360 CA degree intervals therebetween.Routine 1000 may then end.

Returning to 1006, if it is confirmed that the current engine operatingmode is the three-cylinder VDE mode, routine 1000 continues to 1022 todetermine if engine load has increased or if the engine speed is veryhigh. As shown in map 1140, if the engine speed is very high, the enginemay be operated in full-cylinder mode. If the existing operating mode isthe three-cylinder mode, the engine may have previously experiencedmoderate load-moderate speed conditions, or moderate load-high speedconditions. Alternatively, the engine may be at low load-low speedconditions. Therefore, a transition from the existing mode may occurwith an increase in engine load or a significant increase in enginespeed. If an increase in engine load and/or very high engine speed isconfirmed at 1022, routine 1000 progresses to 1024 to transition to anon-VDE mode. Therefore, cylinder 1 may be activated to operate theengine in four-cylinder mode with uneven firing.

If an increase in engine load and/or very high engine speed is notdetermined at 1022, routine 1000 may confirm at 1026 if a decrease inengine load or a change in engine speed has occurred. As explainedearlier, if the engine had previously been operating at moderateload-moderate speed conditions, a decrease in load may enable atransition to two-cylinder VDE mode. In another example, a transition totwo-cylinder VDE mode may also be initiated if an existing low load-lowspeed condition changes to a low load-moderate speed condition. In yetanother example, a transition from a low load-high speed condition to alow load-moderate speed condition may also enable engine operation intwo-cylinder VDE mode. If the change in speed and/or decrease in load isnot determined, routine 1000 progresses to 1012 where the existingengine operating mode may be maintained. However, if a decrease inengine load or a change in engine speed is confirmed, routine 1000continues to 1027 to determine if the changes in speed and/or thedecrease in load are suitable for engine operation in two-cylinder mode.For example, the controller may determine if the existing speed and/orload fall within zone 1126 of Map 1140. If yes, engine operation may betransitioned to two-cylinder VDE mode at 1028. Herein, cylinders 3 and 4may be deactivated and cylinder 1 may be activated while cylinder 2 ismaintained in an active mode. If the decrease in engine load and/orchange in engine speed do not enable operation in two-cylinder mode,routine 1000 continues to 1012 where the existing engine operating modemay be maintained.

Returning to 1008, if it is confirmed that the current engine operatingmode is the two-cylinder VDE mode, routine 1000 continues to 1030 todetermine if engine load has increased or if engine speed has changed.If the existing operating mode is the two-cylinder mode, the engine mayhave previously experienced low to moderate engine loads at moderateengine speeds. Therefore, a transition from the existing mode may occurwith an increase in engine load. A decrease in load may not change theengine operating mode. Further, a change from the existing mode may alsooccur if engine speed decreases to low speed or increases to high (orvery high) speed. If an increase in engine load and/or a change inengine speed is not confirmed at 1030, routine 1000 progresses to 1032to maintain the existing two-cylinder VDE mode.

If an increase in engine load and/or a change in engine speed isconfirmed at 1030, routine 1000 may continue to 1034 to determine if theengine load and/or engine speed enable a transition to three-cylinderVDE mode. For example, engine load may be at moderate levels to enabletransition to three-cylinder VDE mode. If yes, engine operation may betransitioned to three-cylinder VDE mode at 1036. Further, cylinders 3and 4 may be activated and cylinder 1 may be deactivated while cylinder2 is maintained in an active mode. If the engine load and/or enginespeed are not suitable for engine operation in three-cylinder mode,routine 1000 may continue to 1038 to determine if the engine load and/orengine speed enable engine operation in four-cylinder mode. For example,engine load may be very high. In another example, engine speed may bevery high. If yes, at 1040, cylinders 3 and 4 may be activated and theengine may be transitioned to non-VDE mode of operation. Routine 1000may then end. If the increase in engine load and/or change in speed isnot sufficient to operate the engine in full-cylinder mode, routine 1000may return to 1030.

Thus, a controller may determine engine operating modes based on theexisting combination of engine speed and engine load. A map, such asexample Map 1140, may be utilized to decide engine mode transitions.Further, as mentioned in reference to Map 1160 of FIG. 11, in someexamples, the available engine operation modes may be either athree-cylinder mode or a non-VDE mode. A controller may be configured toperform routines, such as the routines of FIGS. 9 and 10, to determinean engine mode of operation and transitions between the two modes basedon an engine load-engine speed map. By operating the engine in one oftwo available modes, transitions in engine operation may be reducedaffording a decrease in torque disturbances and smoother engine control.

Turning now to FIG. 18, it illustrates map 1800 depicting exampletransitions in an engine, such as engine 10, from non-VDE mode to VDEmode. Map 1800 depicts torque demand at plot 1802, mode of engineoperation (two-cylinder VDE mode, three-cylinder VDE mode, and non-VDEmode) at plot 1804, activation status of cylinder 1 at plot 1806,activation status of cylinders 3 and 4 at plot 1808, throttle positionat 1810, and spark advance at plot 1812. All the above parameters areplotted against time on the x-axis. In particular, plot 1812 shows sparkretard as applied to active cylinders. It will also be appreciated thatcylinder 2 is always maintained active and operational in all engineoperating modes. To elaborate further, cylinder 1 herein may be cylinder31 of FIG. 2, cylinder 2 may be cylinder 33 of FIG. 2, cylinder 3 may becylinder 35 of FIG. 2, and cylinder 4 may be cylinder 37 of FIG. 2.

At t0, the engine may be operating in three-cylinder VDE mode because ofmoderate torque demand. Therefore, cylinder 1 may be deactivated whilecylinders 2, 3, and 4 are active and firing at even firing intervals of240 CA degrees. Further, the throttle may be at a position between openand closed while spark advance may be at a timing that provides thedesired torque. At t1, torque demand may increase substantially. Forexample, increased torque demand may occur when a vehicle is beingaccelerated to merge with other vehicles on a highway. In response tothe substantial increase in torque demand, the engine may betransitioned to full-cylinder or non-VDE mode (plot 1804) to provide thedesired torque and accordingly, cylinder 1 may be activated. Further,the throttle may be adjusted to a fully open position to enable higherair flow while spark timing may be maintained at its original setting(e.g., the timing at t0).

At t2, torque demand drops substantially. For example, upon merging ontothe highway, the vehicle may attain cruising speed allowing a reductionin engine speed and engine load. In response to the decrease in torquedemand, and reduction in engine speed and load, the engine may betransitioned to the two-cylinder VDE mode. Further, cylinders 3 and 4may be deactivated while cylinder 1 remains in its active andoperational state. Additionally, the throttle may be moved to a moreclosed position. Between t2 and t3, the throttle may be adjusted towardsa more closed position. A spark retard may also be applied to enablereduction in torque (plot 1812). As shown in FIG. 18, spark advance maybe reduced just prior to the transition at t2 to reduce torque in thenon-VDE mode before changing to two-cylinder mode. In this way, torquein each of the two activated cylinders that are firing after thetransition to two-cylinder VDE mode can be increased so that the totaltorque delivered by the engine does not suddenly drop, but changessmoothly. Once the transition is complete, spark timing may be restored.

At t3, torque demand may slightly increase and the engine may betransitioned to the three-cylinder mode based on an increase in engineload. Accordingly, cylinder 1 may be deactivated, and cylinders 3 and 4may be reactivated simultaneously. Further, throttle position may beadjusted slightly to allow more air flow to meet the increase in torquedemand To reduce a rapid rise in torque, spark timing may be retarded att3. It will be observed that the spark retard applied at t3 may be lowerthan the spark retard applied at t2. The spark timing may be restoredonce desired torque is attained.

In this way, a four cylinder engine may be operated in a three-cylinderVDE mode, a two-cylinder VDE mode, apart from and in addition to a fullcylinder (or non-VDE) mode to attain fuel economy benefits. The systemdescribed herein may comprise an engine including four cylindersarranged inline wherein three of the four cylinders are capable ofdeactivation, a crankshaft with four crank pins, a single balance shaftrotating in an opposing direction to the crankshaft, and a controllerconfigured with computer readable instructions stored on non-transitorymemory for, during a first condition, deactivating two of the threecylinders capable of deactivation, and operating the engine viaactivating two remaining cylinders with even firing. The first conditionmay include low engine load conditions. As described earlier inreference to the example of engine 10 from FIGS. 2, 4, and 5, cylinders31, 35, and 37 may be capable of deactivation while cylinder 33 may notbe capable of deactivation. During the low engine load condition,therefore, cylinders 35 and 37 may be deactivated, and cylinders 31 and33 may be activated with even firing at 360 crank angle degreeintervals.

During a second condition, the controller may also be configured fordeactivating one of the three cylinders capable of deactivation, andoperating the engine via activating remaining three cylinders with evenfiring. Herein, the second condition may be medium engine loads, andcylinder 31 of engine 10 may be deactivated while cylinders 33, 35, and37 are activated to operate the engine in three-cylinder mode. Further,the activated three cylinders (33, 35, and 37) may be fired at about 240crank angle degrees apart from each other. In another example, thesecond condition may include idling conditions.

During a third condition, the controller may be configured for operatingthe engine with all cylinders activated with at least one uneven firingcylinder. Herein, the at least one uneven firing cylinder may be onlycylinder 31 of example engine 10 and the third condition may includehigh and very high engine load conditions. Further, when all cylindersare activated, a first cylinder (e.g., cylinder 35 of engine 10) may befired at 120 degrees of crank rotation, a second cylinder (e.g.,cylinder 33 of engine 10) may be fired at 240 degrees of crank rotationafter firing the first cylinder, a third cylinder (e.g., cylinder 37 ofengine 10) may be fired at 240 degrees of crank rotation after firingthe second cylinder, and a fourth cylinder (e.g., cylinder 31 of engine10) may be fired at 120 degrees of crank rotation after firing the thirdcylinder.

The crankshaft in the example system may include a second crank pin, athird crank pin, and a fourth crank pin positioned 120 degrees apartfrom each other. The crankshaft may further include a first crank pin,situated adjacent to the second crank pin and aligned with the secondcrank pin.

Turning now to FIG. 12, an embodiment with an integrated exhaustmanifold (IEM) with a symmetric exhaust layout for engine 10 isdepicted. Engine components including the cylinders 31, 33, 35, and 37,VCT system 202, CPS system 204 inclusive of camshafts and cams,turbocharger 290, emission control device 70, charge air cooler 90 arethe same as in FIGS. 2 and 4. The exhaust layout from cylinders to theturbocharger is distinct from that shown in FIGS. 2 and 4.

Engine 10 is illustrated with IEM 1220 configured to exhaust combustionproducts from cylinders 31, 33, 35, and 37. IEM 1220 may include exhaustrunners 1239, 1241, 1243 and 1245, each exhaust runner selectivelycommunicating with a corresponding cylinder via one or more exhaustports and exhaust valves of that cylinder. Further, pairs of exhaustrunners may merge within IEM 1220 to form two plenums. As shown in theexample of FIG. 12, exhaust runners 1239 and 1241 may merge atY-junction 1250 into first plenum 1223. Exhaust runners 1243 and 1245may merge at Y-junction 1270 into second plenum 1225. The first plenum1223 and second plenum 1225 may not communicate with each other.

The split exhaust manifold may be integrated into a cylinder head toform IEM 1220. Therefore, exhaust runners 1239, 1241, 1243, and 1245,and exhaust plenums 1223 and 1225 may also be integrated within the IEM1220. Additionally, exhaust runner 1239 and exhaust runner 1241 maymerge within IEM 1220 at Y-junction 1250 such that first plenum 1223originates within IEM 1220. Likewise, exhaust runners 1243 and 1245 mayjoin within IEM 1220 at Y-junction 1270 such that second plenum 1225originates within IEM 1220.

To elaborate further, exhaust runner 1239 may be fluidically coupled tocylinder 31 via exhaust port 20, while exhaust runner 1241 mayfluidically communicate with cylinder 33 via exhaust port 22. Firstplenum 1223 formed by the joining of exhaust runners 1239 and 1241 maythus be fluidically coupled to cylinders 31 and 33. Similarly, exhaustrunner 1243 may be fluidically coupled to cylinder 35 via exhaust port24, while exhaust runner 1245 may fluidically communicate with cylinder37 via exhaust port 26. Second plenum 1225 formed by the joining ofexhaust runners 1243 and 1245 may thus be fluidically coupled tocylinders 35 and 37. As shown in FIG. 12 (and FIGS. 2 and 4), exhaustrunners from cylinders 31 and 33 may not communicate with exhaustrunners from cylinders 35 and 37. Further, first plenum 1223 and secondplenum 1225 may be completely separated, such that blowback from onecylinder may not harm combustion in another cylinder adjacent in thefiring sequence. First and second plenums (1223 and 1225, respectively)may also extend outside of IEM 1220. Thus, the first plenum 1223 andsecond plenum 1225 may be the sole outlets for exhaust outside of IEM1220.

As depicted in FIG. 12, outside of IEM 1220, first plenum 1223 maydeliver exhaust from cylinders 31 and 33 to first scroll 71 of exhaustturbine 92 while second plenum 1225 may direct exhaust from cylinders 35and 37 to second scroll 73 of exhaust turbine 92 via passage 61.Therefore, first scroll 71 may be fluidically coupled only to firstplenum 1223 and second scroll 73 may be fluidically coupled only tosecond plenum 1225.

As in the embodiments of FIGS. 2 and 4, wastegate 69 may be included inbypass passage 67 to allow exhaust in first plenum 1223 to bypassexhaust turbine 92 via passage 65. Exhaust in second plenum 1225 maybypass exhaust turbine 92 via passage 63 and past wastegate 69.

In this way, a system may comprise an integrated exhaust manifold (IEM),an inline group of four cylinders with two inner cylinders, cylinders 33and 35, flanked by two outer cylinders, cylinders 31 and 37. Eachcylinder may fluidically communicate with one of four exhaust runners ofthe IEM, the exhaust runners of a first outer (cylinder 31) and a firstinner cylinder (cylinder 33) merging into first plenum 1223 within theIEM 1220, and the exhaust runners of a second outer (cylinder 37) and asecond inner cylinder (cylinder 35) merging into second plenum 1225within the IEM 1220. The system may also include a turbocharger with atwin scroll exhaust turbine 92 with a first scroll 71 of the turbinefluidically communicating with the first plenum 1223 but not the secondplenum 1225, and second scroll 73 of the turbine fluidicallycommunicating with the second plenum 1225 but not the first plenum 1223.Further, as demonstrated in FIG. 12, the first and second plenums may bethe only exhaust outlets of the IEM and may not fluidically communicatewith each other within the IEM.

An asymmetric exhaust layout with an integrated exhaust manifold, suchas that shown in FIG. 13, may be an alternative to the embodiment ofFIG. 12. Herein, as in FIG. 4, exhaust from cylinder 31 may be separatedand directed to first scroll 71 of exhaust turbine. Meanwhile, exhaustfrom cylinders 33, 35, and 37 may be combined and directed to secondscroll 73 of exhaust turbine 92. The embodiment of FIG. 13 differs fromthe embodiment of FIG. 4 chiefly in regards to the presence of the IEM1220. All other features, including firing patterns and intervalsbetween exhaust pulses may be the same as in the embodiment of FIG. 4.

Exhaust runner 1339 may evacuate exhaust gases from cylinder 31 viaexhaust port 20 and fluidically communicate with first plenum 1323 todirect exhaust pulses to first scroll 71 of exhaust turbine 92. Exhaustrunner 1341 which receives combustion gases from cylinder 33 via exhaustport 22 may combine with exhaust runner 1343, which receives exhaustgases from cylinder 35 via exhaust port 24. Further, exhaust runner1345, which receives exhaust gases from cylinder 37 via exhaust port 26may combine with exhaust runners 1341 and 1343 at Y-junction 1370 toform second plenum 1325. Second plenum 1325 may direct exhaust gasesfrom cylinders 33, 35, and 37 to second scroll 73 of exhaust turbine 92via passage 1361.

In this way, an integrated exhaust manifold (IEM) may be provided toreduce engine weight, surface area, and production costs. By reducingengine weight, fuel economy benefits may be further increased inaddition to those achieved by operating the engine in three-cylinder VDEmode as discussed earlier. Additionally, the turbocharger may bepositioned closer to the cylinders when using an IEM enabling hotterexhaust gases to be discharged into the turbine affording faster warm-upof the emissions control device.

Turning now to FIG. 14, an additional embodiment of engine 10 that maybe operated primarily in three-cylinder mode over a wider range ofengine loads and engine speeds is depicted. Specifically, the engine inthe embodiment of FIG. 14 may include a single cylinder of fourcylinders that is capable of deactivation unlike the engine of FIGS. 2,4, and 5 which includes three cylinders capable of deactivation.Further, the remaining three cylinders in the present embodiment of FIG.14 may be configured to operate with early intake valve closing duringcertain operating conditions. As such, multiple engine components, suchas the turbocharger 290, emission control device 70, etc. describedearlier in reference to FIGS. 2 and 12 may be the same in FIG. 14.Distinct components will be described herein.

As in earlier embodiments, engine 10 of FIG. 14 includes four cylinders:a first outer cylinder 31, a first inner cylinder 33, a second innercylinder 35, and a second outer cylinder 37. In the depicted example,cylinder 31 is capable of deactivation but cylinders 33, 35, and 37 maynot be capable of deactivation. Integrated exhaust manifold (IEM) 1220may assist in exhausting combustion products to turbocharger 290.Further details of the cylinders will be described below. Variable camtiming (VCT) system 202 and cam profile switching (CPS) system 204 maybe included to enable engine operation with variable valve timings andenable the switching of available cam profiles, respectively.

Each cylinder of engine 10 is depicted with two intake valves and twoexhaust valves. Other embodiments may include fewer valves or additionalvalves. Each intake valve is actuatable between an open positionallowing intake air into a respective cylinder and a closed positionsubstantially blocking intake air from the respective cylinder. FIG. 14illustrates intake valves I1-I8 being actuated by the common intakecamshaft 218. Intake camshaft 218 includes a plurality of intake camsconfigured to control the opening and closing of the intake valves. Eachintake valve may be controlled by two intake cams, which will bedescribed further below. In some embodiments, one or more additionalintake cams may be included to control the intake valves. Further still,intake actuator systems may enable the control of intake valves.

Each exhaust valve is actuatable between an open position allowingexhaust gas out of a respective cylinder and a closed positionsubstantially retaining gas within the respective cylinder. FIG. 14shows exhaust valves E1-E8 being actuated by common exhaust camshaft224. Exhaust camshaft 224 includes a plurality of exhaust camsconfigured to control the opening and closing of the exhaust valves. Inthe depicted embodiment, each of the exhaust valves of cylinders 33, 35,and 37 may be controlled by a single exhaust cam, which will bedescribed further below. In some embodiments, one or more additionalexhaust cams may be included to control the exhaust valves. Further,exhaust actuator systems may enable the control of exhaust valves.

Engine 10 of FIG. 14 may be a variable displacement engine wherein onlyone cylinder of the four cylinders 212 may be deactivated, if desired,via one or more mechanisms. As mentioned earlier, cylinder 31 is thesole cylinder including a deactivation mechanism in this embodiment.Intake and exhaust valves of the single cylinder, cylinder 31, may bedeactivated in the VDE mode of engine operation via switching tappets,switching rocker arms, or switching hydraulic roller finger followers.

As in the example of FIG. 2, cylinder 31 in FIG. 14 includes a firstintake cam and a second intake cam per intake valve arranged on commonintake camshaft 218, and a first exhaust cam and a second exhaust camper exhaust valve positioned on common exhaust camshaft 224. Firstintake cams may have a first cam lobe profile for opening the intakevalves for a first intake duration and first valve lift. In the exampleof FIG. 14, first intake cams C1 and C2 of cylinder 31 may open intakevalves I1 and I2 respectively for a similar duration and lift. Secondintake cams, N1 and N2, are depicted as null cam lobes which may have aprofile to maintain their respective intake valves I1 and I2 in theclosed position. Thus, null cam lobes N1 and N2 may assist indeactivating corresponding intake valves when cylinder 31 is deactivatedin the VDE mode.

Similar to the intake valves, cylinder 31 features a first exhaust camand a second exhaust cam arranged on common exhaust camshaft 224. Firstexhaust cams may have a first cam lobe profile providing a first exhaustduration and first exhaust valve lift. First exhaust cams C3 and C4 ofcylinder 31 may have a similar first cam lobe profile which opensrespective exhaust valves E1 and E2 for a given duration and lift. Inother examples, the exhaust durations and lifts provided by cams C3 andC4 may be similar or may be distinct. Second exhaust cams N3 and N4 aredepicted as null cam lobes which may have a profile to maintain theirrespective exhaust valves E1 and E2 in the closed position through oneor more engine cycles. Thus, null cam lobes N3 and N4 may assist indeactivating corresponding exhaust valves in cylinder 31 during the VDEmode.

As mentioned earlier, other embodiments may include different mechanismsknown in the art for deactivating intake and exhaust valves incylinders. Such embodiments may not utilize null cam lobes fordeactivation.

Cylinders 33, 35, and 37 in the embodiment of FIG. 14 may not bedeactivatable enabling engine 10 to operate largely in a three-cylindermode over a wide range of engine speeds and loads. However, duringlighter engine loads, these three cylinders may be operated with earlyintake valve closing (EIVC) to leverage fuel economy benefits arisingfrom reduced pumping losses.

Accordingly, cylinders 33, 35, and 37 may each include a first intakecam and a second intake cam per intake valve arranged on common intakecamshaft 218, and a single exhaust cam per exhaust valve positioned oncommon exhaust camshaft 224. Herein, first intake cams may have a firstcam lobe profile for opening the intake valves for a first intakeduration and first intake valve lift. First intake cams for cylinders33, 35, and 37 may have the same profile as the first intake cams incylinder 31. In other examples, the cams may have distinct profiles.Further, in the depicted example of FIG. 14, second intake cams may havea second cam lobe profile for opening the intake valves for a secondintake duration and lift. The second intake duration may be a shorterintake duration (e.g., shorter than the first intake duration) and alower intake valve lift (e.g., lower than the first intake valve lift).

To elaborate, intake valves I3 and I4 of cylinder 33 may be actuated byeither respective first intake cams C5 and C6, or by respective secondintake cams L5 and L6. Further, intake valves I5 and I6 of cylinder 35may be actuated by either respective first intake cams C9 and C10, or byrespective second intake cams L9 and L10, and intake valves I7 and I8 ofcylinder 37 may be actuated by either respective first intake cams C13and C14, or by respective second intake cams L13 and L14. First intakecams C5, C6, C9, C10, C13, and C14 may have a first cam lobe profileproviding a first intake duration and a first intake valve lift. Secondintake cams L5, L6, L9, L10, L13, and L14 may have a second cam lobeprofile for opening respective intake valves for a second intakeduration different from the first intake duration, and a second intakevalve lift distinct from the first intake valve lift. In the depictedexample, the first intake duration provided by first intake cams C5, C6,C9, C10, C13, and C14 may be longer than second intake duration providedby second intake cams L5, L6, L9, L10, L13, and L14. Additionally, thefirst intake valve lift provided by first intake cams C5, C6, C9, C10,C13, and C14 may be higher than second intake valve lift provided bysecond intake cams L5, L6, L9, L10, L13, and L14.

In one example, the lift and duration provided by the second intake camsfor a given cylinder may be similar. For example, each of the secondintake duration and the second valve lift provided by each of secondintake cams L9 and L10 of cylinder 35 may be the same. To elaborate, theintake duration provided by second intake cam L9 for intake valve 15 maybe the same as the intake duration provided by second intake cam L10 forintake valve 16. In other examples, the lift and duration of the secondintake cams may be distinct on a given cylinder. For example, secondintake cam L5 may have a lower lift and a shorter duration than secondintake cam L6 in order to induce swirl in cylinder 33 during the intakeevent. Likewise, second intake cams L9 and L10 of cylinder 35 may havedifferent profiles from each other, and second intake cams L13 and L14of cylinder 37 may have distinct profiles relative to each other.

Exhaust valves E3-E8 of cylinders 33, 35, and 37 may each be actuated bya single exhaust cam with a first cam profile providing a first exhaustduration and a first exhaust lift. As depicted in FIG. 14, cams C7 andC8 may actuate respective exhaust valves E3 and E4 of cylinder 33, camsC11 and C12 may actuate respective exhaust valves E5 and E6 of cylinder35, and exhaust cams C15 and C16 may actuate respective exhaust valvesE7 and E8 of cylinder 37. The first cam profiles for exhaust camsassociated with cylinders 33, 35, and 37 may be the same as the firstexhaust cam profile of first exhaust cams C3 and C4 in cylinder 31. Inother examples, the cam lobe profiles for exhaust cams may differ.

Each of the intake valves may be actuated by a respective actuatorsystem operatively coupled to controller 12. As shown in FIG. 14, intakevalves I1 and I2 of cylinder 31 may be actuated via actuator system A2,intake valves I3 and I4 of cylinder 33 may be actuated via actuatorsystem A4, intake valves I5 and I6 of cylinder 35 may be actuated viaactuator system A6, and intake valves I7 and I8 of cylinder 37 may beactuated via actuator system A8. Further, each of the exhaust valves maybe actuated by a respective actuator system operatively coupled tocontroller 12. As depicted, exhaust valves E1 and E2 of cylinder 31 maybe actuated via actuator system A1, exhaust valves E3 and E4 of cylinder33 may be actuated via actuator system A3, exhaust valves E5 and E6 ofcylinder 35 may be actuated via actuator system A5, and exhaust valvesE7 and E8 of cylinder 37 may be actuated via actuator system A7.

Other embodiments may include reduced actuator systems or differentcombinations of actuator systems without departing from the scope of thepresent disclosure. For example, the intake valves and exhaust valves ofeach cylinder may be actuated by a single actuator.

CPS system 204 may be configured to translate specific portions ofintake camshaft 218 longitudinally, thereby causing operation of intakevalves I1-I8 to vary between respective first intake cams and secondintake cams (or null cams for cylinder 31).

In an optional embodiment depicted in FIG. 14 (dashed lines) whereinactuator systems A2, A4, A6, and A8 include rocker arms to actuate thefirst and second intake cams, CPS system 204 may be operatively coupledto solenoid S1 and solenoid S2, which in turn may be operatively coupledto the actuator systems. Herein, the rocker arms may be actuated byelectrical or hydraulic means via solenoids S1 and S2 to follow eitherthe first intake cams or the second intake cams. As depicted, solenoidS1 is operatively coupled solely to actuator system A2 (via 1412) andnot operatively coupled to actuator systems A4, A6, and A8. Likewise,solenoid S2 is operatively coupled to actuator systems A4 (via 1422), A6(via 1424), and A8 (via 1426), and not operatively coupled to actuatorsystem A2.

It will be appreciated that though not shown in FIG. 14, solenoids S1and S2 may also be operatively coupled to actuator systems A1, A3, A5,and A7 to actuate the respective exhaust cams. To elaborate, solenoid S1may be operatively coupled only to actuator system A1 and not toactuator systems A3, A5, and A7. Further, solenoid S2 may be operativelycoupled to A3, A5, and A7 but not operatively coupled to A1. Herein,rocker arms may be actuated by electrical or hydraulic means to followeither the first exhaust cams or the second null cams. Alternatively,CPS system 204 may be configured to translate specific portions ofexhaust camshaft 224 longitudinally, thereby causing operation ofexhaust valves E1-E2 to vary between respective first exhaust cams andsecond null cams.

Solenoid S1 may control intake cams of intake valves I1 and I2 ofcylinder 31 via rocker arms in actuator system A2. As mentioned earlier,though not shown in FIG. 14, solenoid S1 may also control exhaust valvesE1 and E2 of cylinder 31, which may be deactivated at the same time asintake valves I1 and 12. A default position for solenoid S1 may be aclosed position such that rocker arm(s) operatively coupled to solenoidS1 are maintained in a pressureless unlocked position resulting in nolift (or zero lift) of intake valves I1 and I2.

Solenoid S2 may control each pair of intake cams of intake valves I3 andI4 of cylinder 33, intake valves I5 and I6 of cylinder 35, and intakevalves I7 and I8 of cylinder 37 respectively. Solenoid S2 may controlthe intake cams of intake valves of cylinders 33, 35, and 37 via rockerarms in respective actuator systems A4, A6, and A8. Solenoid S2 may bemaintained in a default closed position such that associated rocker armsare maintained in a pressureless locked position.

In this way, CPS system 204 may switch between a first cam for opening avalve for a first duration, and a second cam, for opening the valve fora second duration. In the given example, CPS system 204 may switch camsfor intake valves in cylinders 33, 35, and 37 between a first cam foropening the intake valves for a first longer duration, and a secondintake cam for opening the intake valves for a second shorter duration.CPS system 204 may switch cams for intake valves in cylinder 31 betweena first cam for opening the intake valves for a first duration (that maybe similar to the first intake duration in cylinders 33, 35, and 37) anda second null cam for maintaining intake valves closed. Further, CPSsystem 204 may switch cams for exhaust valves in only cylinder 31between a first cam for opening the exhaust valves for a first duration,and a second null cam for maintaining exhaust valves closed. In theexample of cylinders 33, 35, and 37, CPS system 204 may not switch camsfor the exhaust valves as cylinders 33, 35 and 37 are configured withone cam per exhaust valve.

CPS system 204 may receive signals from controller 12 to switch betweendifferent cam profiles for different cylinders in engine 10 based onengine operating conditions. For example, during high engine loads,engine operation may be in non-VDE mode. Herein, all cylinders may beactivated and the intake valves in each cylinder may be actuated bytheir respective first intake cams.

In another example, at a medium engine load, engine 10 may be operatedin a three-cylinder mode. Herein, CPS system 204 may be configured toactuate the intake valves of cylinders 33, 35, and 37 with theirrespective first intake cams. Concurrently, cylinder 31 may bedeactivated by CPS system 204 via actuating its intake and exhaustvalves with respective second, null cams. In yet another example, at alow engine load, engine 10 may be operated in a three-cylinder mode withearly intake valve closing. Herein, CPS system 204 may be configured toactuate the intake valves of cylinders 33, 35, and 37 with theirrespective second intake cams which provide shorter intake durations.

In the optional embodiment comprising actuator systems with rocker armswherein the rocker arms are actuated by electrical or hydraulic means,the engine may be operated with three active cylinders and early intakevalve closing by energizing solenoid S2 coupled to cylinders 33, 35, and37 to open and actuate the respective rocker arms to follow the secondintake cams with shorter intake duration. At medium engine loads,solenoid S2 may be de-energized to close such that the respective rockerarms follow the first intake cams with longer intake duration in thethree active cylinders (33, 35, and 37). In both VDE modes (with earlyintake valve closing and without early intake valve closing), solenoidS1 may be maintained in its default position. In non-VDE mode, solenoidS1 may be energized to open so that respective rocker arms follow thefirst intake cams (and first exhaust cams, when applicable) on cylinder31, and solenoid S2 may be de-energized to close such that therespective rocker arms follow the first intake cams with longer intakeduration in cylinders 33, 35, and 37. Thus, FIG. 14 describes an enginesystem including four cylinders arranged inline, wherein each cylindermay have at least one intake valve. The intake valve(s) of a singlecylinder (cylinder 31) may be actuated by one of two cams, wherein afirst cam has a non-zero lift profile and a second cam has a zero liftprofile. Herein, the second cam may be a null cam lobe with a no-lift ora zero lift profile. Further, each of the intake valves of remainingthree cylinders (cylinders 33, 35, and 37) may be actuated by one of twocams, where both cams have non-zero lift profiles. Accordingly, each cammay lift its respective intake valve to a non-zero height and none ofthe cams actuating either intake or exhaust valves in cylinders 33, 35,and 37 may be null cam lobes.

Engine 10 of embodiment in FIG. 14 may be operated in either a non-VDEmode or a VDE mode. During the VDE mode, cylinder 31 may be disabled bydeactivating its intake and exhaust valves. Herein, intake valves I1 andI2, and exhaust valves E1 and E2 may be actuated (or closed) by theirrespective null cam lobes. The VDE mode may be a three-cylinder mode.Two three-cylinder VDE modes may be available to engine 10 based on aselection of either the first intake cam or the second intake cam in thethree active cylinders. Specifically, a first three-cylinder VDE modemay include engine operation with longer intake durations via usingfirst cam lobes to actuate each of the intake valves in cylinders 33,35, and 37. Engine 10 may operate in the first three-cylinder VDE mode,without early intake valve closing (EIVC), during medium engine loadconditions. A second three-cylinder VDE mode may include engineoperation with a shortened intake duration (e.g., EIVC) by using thesecond cam lobes to actuate each of the intake valves in cylinders 33,35, and 37. The second three-cylinder VDE mode may, therefore, includeEIVC and may be used for engine operation during engine idlingconditions and during low engine load conditions. As stated earlier,during both VDE modes, cylinder 31 may be deactivated. CPS system 204may switch between the first cam lobes and the second cam lobes forintake valve actuation in the VDE mode to enable a first three-cylinderVDE mode or a second three-cylinder VDE mode based on engine operatingconditions.

Specifically, during the first three-cylinder VDE mode, intake valves incylinders 33, 35, and 37 may be actuated by first cams C5, C6, (forintake valves I3-I4) and C9, C10, (for intake valves I5-I6) and C13, C14(for intake valves I7-I8). During the second three-cylinder VDE mode,intake valves in cylinders 33, 35, and 37 may be actuated by respectivesecond cams L5, L6, and L9, L10, and L13, L14.

In the non-VDE mode, the CPS system 204 may switch to first cam lobesfor actuating all intake valves in all cylinders with a longer intakeduration and a higher intake valve lift. The non-VDE mode may beutilized during high or very high engine load conditions. To elaborate,during the non-VDE mode, intake valves and exhaust valves in cylinder 31may be actuated by cams C1, C2 (for I1-I2), and C3 and C4 (for E1-E2)while intake and exhaust valves in cylinders 33, 35, and 37 may beactuated by first cams C5, C6 (for I3-I4), C7, C8 (for E3-E4), C9, C10(for I5-I6), C11, C12 (for E5-E6), C13, C14 (for I7-I8), C15, and C16(for E7-E8).

Referring now to FIG. 15, map 1500 depicts an example intake valve andexhaust valve operation utilizing cam profile switching between the twonon-zero lift cam lobes described above with reference to FIG. 14. Inparticular, FIG. 15 shows the operation of an intake valve (which may beone of intake valves I3-I8) and an exhaust valve (which may be one ofexhaust valves E3-E8), with respect to crankshaft angle.

Map 1500 illustrates crank angle degrees plotted along the x-axis andvalve lift in millimeters plotted along the y-axis. An exhaust stroke ofthe cycle is shown generally occurring between 180 degrees and 360degrees crank angle. Subsequently, a regular intake stroke of the cycleis shown generally occurring between 360 degrees and 540 degrees crankangle. The regular intake stroke may occur with a first cam actuatingthe intake valves of cylinders 33, 35, or 37.

Further, as shown in map 1500, each of the exhaust valve and the intakevalve have a positive lift which corresponds to the valves being in anopen position, thereby enabling air to flow out of or into thecombustion chamber. During engine operation, the amount of lift duringintake strokes and exhaust strokes may vary from that shown in FIG. 15without departing from the scope of the examples described herein.

Curve 1510 depicts an example exhaust valve timing, lift, and durationfor an exhaust valve in cylinder 33, cylinder 35, or cylinder 37.Exhaust valve opening (EVO) may commence before 180 crankshaft degrees,at approximately 120 crankshaft degrees, and exhaust valve closing (EVC)may end at approximately 380 crankshaft degrees. Therefore, exhaustduration may be approximately 260 crankshaft degrees. In one example,exhaust duration may be 250 crankshaft degrees. In another example,exhaust duration may be longer at 270 crankshaft degrees. In yet anotherexample, exhaust duration may be exactly 260 crank angle degrees.Further, exhaust valve lift may be approximately 9 mm.

Curve 1520 portrays an example intake valve timing, lift, and durationfor an intake valve actuated by a first cam in cylinder 33, cylinder 35or cylinder 37. Herein, intake valve opening (IVO) may begin atapproximately 350 crankshaft degrees and intake valve closing (IVC) mayoccur at approximately 590 crankshaft degrees. Accordingly, intakeduration when actuating with the first cam may be approximately 240crank angle degrees. In one example, intake duration may be 230crankshaft degrees. In another example, intake duration may be longer at260 crankshaft degrees. In yet another example, intake duration may beexactly 240 crankshaft degrees. Further, intake valve lift may beapproximately 9 mm. In one example, intake valve lift may be 8 mmwhereas in another example, intake valve lift may be 10 mm. In yetanother example, intake valve lift may be exactly 9 mm. Intake andexhaust valve lifts may vary from that stated herein without departingfrom the scope of the examples herein.

Curve 1530 depicts an example intake valve timing, lift, and durationfor an intake valve actuated by a second cam in cylinder 33, cylinder35, or cylinder 37. Herein, intake valve opening (IVO) may begin atabout the same time as in curve 1520, e.g., at approximately 350crankshaft degrees. However, the intake valve may be closed earlier andearly intake valve closing (EIVC) may occur at approximately 470crankshaft degrees. Accordingly, intake duration when actuating with thesecond cam may be approximately 120 crank angle degrees. In one example,intake duration may be shorter e.g., 110 crankshaft degrees. In anotherexample, intake duration may be longer e.g., 140 crankshaft degrees. Inyet another example, intake duration may be exactly 120 crank angledegrees. Further, intake valve lift may be approximately 3 mm. Intakevalve lift during EIVC may vary between 2 mm to 5 mm in alternateexamples.

As depicted in FIG. 15, bracket 1572 represents an exhaust duration,bracket 1574 represents an intake duration with first cam, and bracket1576 represents an intake duration with second cam actuation. As will beobserved, bracket 1576 is substantially shorter than bracket 1574. Asdescribed earlier, intake duration with second cam actuation may beapproximately 120 crank angle degrees, and shorter than intake durationwith first cam actuation which may be approximately 240 crank angledegrees. Further, intake valve lift with second cam is lower than intakevalve lift with first cam.

Turning now to FIG. 16, it shows an example routine 1600 for determininga mode of operation in a vehicle with an engine, such as the exampleengine of FIG. 14. Specifically, a three-cylinder VDE mode with earlyintake valve closing (EIVC), a three-cylinder VDE mode without EIVC or anon-VDE mode of operation may be selected based on engine loads.Further, transitions between these modes of operation may be determinedbased on changes in engine loads. Routine 1600 may be controlled by acontroller such as controller 12 of engine 10.

At 1602, the routine includes estimating and/or measuring engineoperating conditions. These conditions may include, for example, enginespeed, engine load, desired torque, manifold pressure (MAP), air/fuelratio, mass air flow (MAF), boost pressure, engine temperature, sparktiming, intake manifold temperature, knock limits, etc. At 1604, theroutine includes determining a mode of engine operation based on theestimated engine operating conditions. For example, engine load may be asignificant factor to determine engine mode of operation which includesa three-cylinder VDE mode with EIVC, a three cylinder VDE mode withoutEIVC at regular, base durations of intake, or a non-VDE mode (orfour-cylinder mode). The regular, base durations of intake in thethree-cylinder mode without EIVC may be longer than the intake durationsduring the three-cylinder mode with EIVC. In another example, desiredtorque may also determine engine operating mode. A higher demand fortorque may include operating the engine in non-VDE or four-cylindermode. A lower demand for torque may enable a transition of engineoperation to a VDE mode. As will be elaborated later in reference to map1180 of FIG. 11, a combination of engine speed and engine loadconditions may determine engine mode of operation.

At 1606, therefore, routine 1600 may determine if high (or very high)engine load conditions exist. For example, the engine may beexperiencing higher loads as the vehicle ascends a steep incline. Inanother example, an air-conditioning system may be activated therebyincreasing load on the engine. If it is determined that high engine loadconditions exist, routine 1600 continues to 1608 to activate allcylinders and operate in the non-VDE mode. In the example of engine 10of FIG. 14, all four cylinders may be activated during the non-VDE mode.As such, a non-VDE mode may be selected during very high engine loadsand/or very high engine speeds.

At 1610, the four cylinders may be fired in the following sequence:1-3-2-4 with cylinders 2, 3, and 4 firing about 240 CA degrees apart,and cylinder 1 firing about halfway between cylinder 4 and cylinder 3.In this example, cylinder 31 of FIG. 14 is cylinder 1, cylinder 33 ofFIG. 14 is cylinder 2, cylinder 35 of FIG. 14 is cylinder 3, andcylinder 37 of FIG. 14 is cylinder 4. When all cylinders are activated,the single deactivatable cylinder 1 (cylinder 31) may be firedapproximately midway between cylinder 4 and cylinder 3. Further, firingevents in cylinder 4 may be separated from firing events in cylinder 3by 240 crank angle degrees. Thus, cylinder 1 may be fired approximately120 crank angle degrees after cylinder 4 is fired, and approximately 120crank angle degrees before cylinder 3 is fired. Furthermore, cylinder 2may be fired about 240 crank angle (CA) degrees after firing cylinder 3and cylinder 4 may be fired about 240 crank angle degrees after firingcylinder 2. Thus the non-VDE mode includes uneven firing intervals(e.g., 120°-240°-240°-120°) wherein cylinder 3 is fired 120 CA degreesafter cylinder 1, cylinder 2 is fired 240 CA degrees after cylinder 3,cylinder 4 is fired 240 CA degrees after cylinder 2, and cylinder 1 isfired at 120 CA degrees after cylinder 1. The sequence continues thereonat the same firing intervals in non-VDE mode.

If at 1606, it is determined that high engine load conditions do notexist, routine 1600 progresses to 1612 where it may determine if lowengine load conditions are present. For example, the engine may beoperating at a light load when cruising on a highway. In anotherexample, lower engine loads may occur when the vehicle is descending anincline. If low engine load conditions are determined at 1612, routine1600 continues to 1614 to operate the engine in a three-cylinder VDEmode with EIVC. Herein, cylinder 1 may be deactivated. As explained inreference to FIG. 15, the three-cylinder mode with EIVC may includeactuating the intake valves with respective second cams. Therefore, thethree activated cylinders may be operated with an intake duration of 120crank angle degrees at 1616, and with an intake valve lift of 3 mm at1618. Additionally, at 1620, the three activated cylinders (cylinders 2,3, and 4) may be fired at 240 crank angle degree intervals. Routine 900may then proceed to 1632.

If it is determined at 1612 that low engine load conditions are notpresent, routine 1600 progresses to 1622 where it may determine engineoperation under medium loads. Next, at 1624, the engine may be operatedin a three-cylinder VDE mode without EIVC wherein cylinder 1 may bedeactivated and cylinders 2, 3, and 4 may be activated. Herein, theintake valves of the activated cylinders may be actuated via theirrespective first cams. Further, at 1626, intake durations in the threeactivated cylinders may be 240 crank angle degrees, and at 1628, intakevalves may be lifted to about 9 mm. Further still, at 1630, combustionevents in the three activated cylinders may occur at 240 crank angledegree intervals.

Once an engine operating mode is selected and engine operation inselected mode is commenced (e.g., at one of 1610, 1624, or 1614),routine 1600 may determine at 1632 if a change in engine load isoccurring. For example, the vehicle may complete ascending the inclineand reach a level portion whereby the existing high engine load may bereduced to a moderate load. In another example, the vehicle mayaccelerate on the highway to pass other vehicles. Herein, engine loadmay increase to a moderate or high load. If it is determined at 1632that a change in load is not occurring, routine 1600 continues to 1634to maintain engine operation in the selected mode. Else, at 1636, engineoperation may be transitioned to a different mode based on the change inengine load. Mode transitions will be described in detail in referenceto FIG. 17 which shows an example routine 1700 for transitioning from anexisting engine operation mode to a different operation mode based ondetermined engine loads.

At 1638, various engine parameters may be adjusted to enable a smoothtransition and reduce torque disturbance during transitions. Forexample, when transitioning from a VDE mode to a non-VDE mode, anopening of an intake throttle may be decreased to allow the MAP todecrease. Since the number of firing cylinders may have increased in thetransition from VDE mode to non-VDE mode, the airflow and thus, MAP toeach of the firing cylinders, may need to be decreased to minimizetorque disturbances. Therefore, adjustments may be made such that theintake manifold may be filled to a lesser extent with air to achieve anair charge and MAP that will provide the driver-demanded torque as soonas the cylinders are reactivated. Accordingly, based on an estimation ofengine operating parameters, the engine's throttle may be adjusted toreduce airflow and the MAP to a desired level. Additionally oralternatively, spark timing may be retarded to maintain a constanttorque on all the cylinders, thereby reducing cylinder torquedisturbances. When sufficient MAP is reestablished, spark timing may berestored and throttle position may be readjusted. In addition tothrottle and spark timing adjustments, valve timing may also be adjustedto compensate for torque disturbances. Routine 1600 may end after 1638.

Turning now to map 1180 of FIG. 11, it shows an engine speed-engine loadmap for the embodiment of the engine in FIG. 14. Specifically, map 1180indicates different engine operation modes that are available atdifferent combinations of engine speeds and engine loads. Map 1180 alsoshows engine speed plotted along the x-axis and engine load plottedalong the y-axis. Line 1122 represents a highest load that a givenengine can operate under at a given speed. Zone 1124 indicates afour-cylinder non-VDE mode for a four-cylinder engine, such as engine 10described earlier. Zone 1148 indicates a three-cylinder VDE mode withoutEIVC and zone 1182 indicates a three-cylinder VDE mode with EIVC.

Map 1180 depicts an example of engine operation where the engine maylargely operate in one of two available three-cylinder VDE modes. Atwo-cylinder VDE mode option is not available for engine 10 of FIG. 14.Engine 10 may operate in three-cylinder VDE mode with EIVC during lowengine loads-low engine speeds, during low engine loads-moderate enginespeeds, and during low engine loads-high engine speeds. Engine mode ofoperation may be transitioned to three-cylinder mode without EIVC duringmedium engine load conditions at all speeds other than very high, asshown by zone 1148. At very high speed conditions at all loads and veryhigh load conditions at all engine speeds, a non-VDE mode of operationmay be utilized.

It will be appreciated from Map 1180 that the example engine of FIG. 14may operate substantially in a three-cylinder mode. A non-VDE mode maybe selected only during the high load and high engine speed conditions.Thus, fuel economy may be enhanced while reducing the number oftransitions between three-cylinder mode and non-VDE mode. In the exampleshown in Map 1180, transitions between non-VDE and VDE modes may besignificantly reduced. By reducing transitions in engine operatingmodes, engine control may be easier and torque disturbances due to suchtransitions may be lessened. Further, in the example of engine 10, asingle cylinder may be arranged to be capable of deactivation enabling adecrease in costs. The fuel economy benefits may be relativelydiminished in comparison to the engine operation example of Map 1140.

Thus, a method for an engine is provided comprising during a firstcondition, operating the engine with a single cylinder deactivated andremaining cylinders activated with a first intake duration, during asecond condition, operating the engine with the single cylinderdeactivated and the remaining cylinders activated with a second intakeduration, and during a third condition, operating the engine with allcylinders activated. Herein, the first condition may include a firstengine load, the second condition may include a second engine load, andthe third condition may include a third engine load, such that thesecond engine load is lower than the first engine load, and the firstengine load is lower than the third engine load. The method may furthercomprise during the first condition operating the remaining cylinderswith a first intake valve lift, and during the second condition,operating the remaining cylinders with a second intake valve lift.Further, during the third condition, all cylinders may be activated withthe first intake duration and the first intake valve lift. Herein, thefirst intake valve lift may be higher than the second intake valve liftand the first intake duration may be longer than the second intakeduration. Further, the first intake duration may be approximately 240crank angle degrees, and the second intake duration may be approximately120 crank angle degrees. The exhaust duration may be the same during allthree conditions and may be approximately 260 crank angle degrees.Further, the second condition may include an idling engine condition.

The method may further include switching between the first condition andthe second condition with a cam profile switching system between a firstcam and a second cam, the first cam for opening a first intake valve ofeach of the remaining cylinders for the first intake duration, and thesecond cam for opening the first intake valve of each of the remainingcylinders for the second intake duration. Herein, the engine maycomprise four cylinders arranged inline. Further, during the first andsecond conditions, firing events in the engine may be separated by 240crank angle degrees. During the third condition, the single cylinder maybe fired approximately midway between a fourth cylinder and a thirdcylinder, and wherein the fourth cylinder and the third cylinder may befired 240 crank angle degrees apart. The method may further comprisefiring a second cylinder approximately 240 crank degrees after firingthe third cylinder.

Turning now to FIG. 17, routine 1700 for determining transitions inengine operating modes based on engine load conditions is described forthe example engine of FIG. 14. Specifically, the engine may betransitioned from a non-VDE mode to one of two three-cylinder VDE modesand vice versa, and may also be transitioned between the twothree-cylinder VDE modes.

At 1702, the current operating mode may be determined. For example, thefour-cylinder engine may be operating in a non-VDE, full cylinder mode,a three-cylinder VDE mode with EIVC, or a three-cylinder VDE modewithout EIVC. At 1704, it may be determined if the engine is operatingin the four-cylinder mode. If not, routine 1700 may move to 1706 todetermine if the current mode of engine operation is the three-cylinderVDE mode without EIVC. If not, routine 1700 may determine at 1708 if theengine is operating in the three-cylinder VDE mode with EIVC. If not,routine 1700 returns to 1704.

At 1704, if it is confirmed that a non-VDE mode of engine operation ispresent, routine 1700 may continue to 1710 to confirm if engine load hasdecreased. If the existing engine operating mode is a non-VDE mode withall four cylinders activated, the engine may be experiencing high orvery high engine loads. In another example, a non-VDE mode of engineoperation may be in response to very high engine speeds. Thus, if theengine is experiencing high engine loads to operate in a non-VDE mode, achange in operating mode may occur solely with a decrease in load. Anincrease in engine load may not change operating mode.

If it is confirmed that a decrease in load has not occurred, at 1712,the existing engine operating mode may be maintained and routine 1700ends. However, if it is determined that a decrease in engine load hasoccurred, routine 1700 progresses to 1714 to determine if the decreasein engine load is to a medium load. In another example, a change inengine conditions may include a decrease in load to medium loads and adecrease in speed to high, moderate or low speeds. As described earlierin reference to Map 1180 of FIG. 11, a transition to moderateload-moderate speed conditions, and to moderate load-low speedconditions may enable engine operation in three-cylinder VDE modewithout EIVC. It will be appreciated that a transition to three-cylinderVDE mode without EIVC may also occur during moderate load-high speedconditions. Accordingly, if a decrease to medium load is confirmed, at1716, a transition to three-cylinder VDE mode without EIVC may occur.Herein, cylinder 1 of the four cylinders may be deactivated whilemaintaining remaining three cylinders in an activated condition.Further, intake valves in the remaining three cylinders may be actuatedby their respective first cams providing a longer intake duration.Routine 1700 may then end.

If at 1714 it is determined that the decrease in engine load is not to amedium engine load condition, routine 1700 continues to 1718 to confirmthat the decrease in engine load is to a low load condition. Asexplained above in reference to Map 1180 of FIG. 11, low engine loadswith low to high engine speeds may enable a three-cylinder VDE mode withEIVC. If the decrease in load is not to a low load condition, routine1700 returns to 1710. Else, at 1720 a transition to the three-cylinderVDE mode with EIVC may be completed by deactivating cylinder 1 andmaintaining cylinders 2, 3, and 4 in an activated condition. Further,intake valves in the activated three cylinders may be actuated by theirrespective second cams providing shorter intake durations. Routine 1700may then end.

Returning to 1706, if it is confirmed that the current engine operatingmode is the three-cylinder VDE mode without EIVC, routine 1700 continuesto 1722 to determine if engine load has increased. If the existingoperating mode is the three-cylinder mode without EIVC, the engine mayhave previously experienced moderate load conditions. Therefore, atransition from the existing mode may occur with an increase in engineload or a significant increase in engine speed. A transition from theexisting mode may also occur if there is a decrease in engine load to alow load. If an increase in engine load is confirmed at 1722, routine1700 progresses to 1724 to transition to a non-VDE mode. Therefore,cylinder 1 may be activated to operate the engine in four-cylinder mode.Further, intake valves in all cylinders may be actuated by theirrespective first cams providing a longer intake duration.

If an increase in engine load is not determined at 1722, routine 1700may confirm at 1726 if a decrease in engine load has occurred. If yes,engine operation may be transitioned to three-cylinder VDE mode withEIVC at 1728. The CPS system may switch intake valve actuating cams froma first cam with longer intake duration to a second cam with a shorterintake duration. If a decrease in engine load is not confirmed, routine1700 may continue to 1712 where the existing engine operating mode maybe maintained. Herein, the existing engine operating mode is thethree-cylinder VDE mode without EIVC.

Returning to 1708, if it is confirmed that the current engine operatingmode is the three-cylinder VDE mode with EIVC, routine 1700 continues to1730 to determine if engine load has increased. If the existingoperating mode is the three-cylinder VDE mode with EIVC, the engine mayhave previously experienced lighter engine loads. Therefore, atransition from the existing mode may occur with an increase in engineload to either medium, high or very high. In another example, atransition may also occur if engine speed increases to very high speeds.If an increase in engine load is not confirmed at 1730, routine 1700progresses to 1732 to maintain the existing three-cylinder VDE mode withEIVC. It should be noted that the relative speed (or loads or other suchparameters) as being high or low refer to the relative speed compared tothe range of available speeds.

If an increase in engine load is confirmed at 1730, routine 1700 maycontinue to 1734 to determine if the increase in engine load is to amedium load (from an existing low load). If yes, engine operation may betransitioned to three-cylinder VDE mode without EIVC at 1736. The CPSsystem may switch intake valve actuating cams from the second cam withshorter intake duration to the first cam with longer intake duration. Ifan increase to medium engine load is not confirmed, routine 1700 maycontinue to 1738 to determine if the increase in load is to a high (orvery high load). If yes, at 1740, cylinder 1 may be activated and theengine may be transitioned to non-VDE mode of operation. Further, theintake valves in all cylinders may be actuated via their respectivefirst intake cams providing longer intake durations. Routine 1700 maythen end. If the increase in engine load is not to a high (or very high)load, routine 1700 may return to 1730.

Thus, the embodiment of FIG. 14 may comprise an engine with fourcylinders wherein a single cylinder of the four cylinders includes adeactivation mechanism. Further, each of the remaining three of the fourcylinders (excluding the single cylinder) include at least one intakevalve actuatable between an open position and a closed position via afirst intake cam having a first profile for opening the intake valve fora first intake duration, and via a second intake cam having a secondprofile for opening the intake valve for a second intake duration.Additionally, the engine may include a controller with computer-readableinstructions stored in non-transitory memory for during a low engineload, deactivating the single cylinder, and actuating the intake valveof each of the remaining three cylinders with the second intake cam.During a medium engine load, the controller may deactivate the singlecylinder, and actuate the intake valve of each of the remaining threecylinders with the first intake cam, and during a high engine load, thecontroller may activate the single cylinder, and actuate the intakevalve of each of the remaining three cylinders with the first intakecam. Herein, the first intake cam may have a profile that enables alonger intake duration than the intake duration enabled by the secondintake cam. Therefore, the first intake duration is longer than thesecond intake duration. Furthermore, the first profile of the firstintake cam may have a first valve lift and the second profile of thesecond intake cam may have a second valve lift wherein the second valvelift is lower than the first valve lift. In other words, the first valvelift if higher than the second valve lift.

In this way, an engine with variable displacement engine (VDE) operationmay be operated for substantial reduction in fuel consumption andsmoother engine control. The engine may include a crankshaft thatenables a three-cylinder VDE mode with even firing such that three offour cylinders are fired about 240 crank angle degrees apart from eachother. Herein, a single cylinder of the four cylinders may bedeactivated. The engine may also operate in full-cylinder or non-VDEmode wherein all four cylinders are activated with uneven firing. In oneexample, the crankshaft may enable the single cylinder to be firedapproximately midway between two of the three cylinders. The unevenfiring mode may comprise firing the single cylinder at approximatelyzero crank angle (CA) degrees followed by firing a first of the threecylinders approximately 120 CA degrees after firing the single cylinder.A second of the three cylinders may be fired approximately 240 CAdegrees after firing the first of the three cylinders followed by firinga third of the three cylinders approximately 240 CA degrees after firingthe second of the three cylinders. For example, in a four-cylinderengine with cylinders 1, 2, 3, 4 arranged inline, the firing order infull-cylinder mode may be 1-3-2-4 wherein cylinders 2, 3, and 4 fire 240CA degrees apart from each other and cylinder 1 fires approximatelymidway between cylinder 4 and cylinder 3.

The engine described above may either be a naturally aspirated engine ora turbocharged engine. In the example of a turbocharged engine with VDEoperation having a firing order 1-3-2-4, a twin scroll exhaust turbinemay be included to separate exhaust pulses. Exhaust runners fromcylinder 1 and cylinder 2 may be coupled to a first scroll of theexhaust turbine and exhaust runners from cylinder 3 and cylinder 4 maybe coupled to a second scroll of the exhaust turbine. Each scroll maythus receive exhaust pulses separated by at least 240 CA degrees. Asymmetric layout such as the one described above may improve turbineefficiency. An alternate layout may comprise coupling the exhaust runnerfrom cylinder 1 to the first scroll of the exhaust turbine and couplingexhaust runners from cylinders 2, 3, and 4 to the second scroll of theexhaust turbine. This layout may also provide exhaust pulse separationof at least 240 CA degrees in each scroll but may result in a relativelylower turbine efficiency. However, each of these layouts may offer acompactness which may be utilized by integrating the exhaust manifoldinto the cylinder head. By including an integrated exhaust manifold, theengine may have reduced weight, reduced surface area, and decreasedexpenses.

In another embodiment, the engine may be capable of operating in atwo-cylinder VDE mode during low (or lower) engine load conditions. Inthis embodiment, only three of the four cylinders may be provided withdeactivation mechanisms. The single uneven firing cylinder (duringfull-cylinder mode) may be one of the three provided with deactivationmechanisms. For example, cylinders 1, 3, and 4 may be deactivatablewhile cylinder 2 may not be deactivatable. To operate in thetwo-cylinder VDE mode, the single uneven firing cylinder may beactivated along with the non-deactivatable cylinder. For example,cylinder 1 and cylinder 2 may be activated in the two-cylinder VDE modewhile cylinder 3 and cylinder 4 may be deactivated. Further, the enginemay be operated with even firing wherein the two activated cylinders(cylinders 1 and 2) are fired at approximately 360 CA degree intervalsfrom each other. In this embodiment, the engine may be operated in thetwo-cylinder VDE mode during lower engine loads, as mentioned above. Theengine may be transitioned to three-cylinder VDE mode during mediumengine load conditions. Further, a higher engine load condition mayinclude engine operation in full-cylinder or non-VDE mode. Additionally,during idle, the engine may be operated in the three-cylinder VDE mode.It will be noted that engine load conditions mentioned above arerelative. As such, low engine load conditions may include conditionswhere engine load is lower than each of medium engine loads and high (orhigher) engine loads. Medium engine loads include conditions whereengine load is greater than low load conditions, but lower than high (orhigher) load conditions. High or very high engine load conditionsinclude engine loads that may be higher than each of medium and low (orlower) engine loads.

In yet another embodiment, the engine may not be capable of operating ina two-cylinder VDE mode. Herein, during lower engine loads the enginemay operate in a three-cylinder mode with early intake valve closing(EIVC). In this embodiment, the single uneven firing cylinder may be theonly cylinder including a deactivation mechanism. The remaining threecylinders may include intake valves that are actuatable by two cams: afirst cam providing a longer intake duration and a higher valve lift,and a second cam providing a shorter intake duration and a lower valvelift. Herein, the second cam may enable EIVC operation. A controller ofthe engine in this embodiment may operate the engine in three-cylinderVDE mode with EIVC during lighter engine loads, and may transitionengine operation to a three-cylinder mode without EIVC during moderateengine loads. In some examples, the engine may be operated during higherengine load conditions in the three-cylinder mode without EIVC. Finally,during very high engine loads, the controller may transition engineoperation to non-VDE (full-cylinder) mode and activate the singlecylinder. It will be appreciated that the three cylinder VDE modeincludes even firing wherein the engine is fired at approximately 240 CAdegree intervals. Further, in the non-VDE mode, an uneven firing patternmay be used.

In this way, a three cylinder VDE mode may be used primarily for engineoperation in the engine embodiments described above. Aside from fueleconomy benefits, the engine may operate with decreased NVH offeringimproved drivability. A single balance shaft may replace the typicaltwin balance shafts to counter crankshaft rotation and offset vibrationsproviding a reduction in weight and decreased frictional losses.Accordingly, fuel economy may be further enhanced. An integrated exhaustmanifold (IEM) may also be used in the described embodiments providing afurther decline in engine weight. In the example of a turbochargedengine having VDE operation with a twin scroll turbocharger, exhaustpulse separation may be obtained which may result in higher volumetricefficiencies and engine power. In the example of the engine capable ofthree-cylinder VDE mode with EIVC, the engine may be primarily operatedin a three-cylinder VDE mode. Thus, fuel consumption may be decreasedand enhanced engine efficiency may be attained. Further, by using atwo-step intake valve lift, charge motion in the cylinders may beincreased and pumping losses may be reduced. In addition, transitionsbetween the VDE and non-VDE modes may be reduced resulting in smootherengine operation and improved engine control. Overall, the engineembodiments with VDE operation described herein offer substantial fueleconomy benefits and enhances drivability.

In one representation, a method for an engine having VDE operation maycomprise when all cylinders are activated, firing a first cylinder at120 degrees of crank rotation, firing a second cylinder at 240 degreesof crank rotation after firing the first cylinder, firing a thirdcylinder at 240 degrees of crank rotation after firing the secondcylinder, firing a fourth cylinder at 120 degrees of crank rotationafter firing the third cylinder. Further, when three cylinders areactivated, the method may include firing the three activated cylindersat 240 crank angle degree intervals. In one example, the three cylindersmay be activated during idle engine conditions. In another example, thethree cylinders may be activated during medium engine load conditions.The method may also comprise when two cylinders are activated, firingthe two activated cylinders at 360 crank angle degree intervals. The twocylinders may be activated during low engine load conditions.

In another representation, a system for an engine may comprise aturbocharger for providing a boosted aircharge to the engine, theturbocharger including an intake compressor and an exhaust turbine, theexhaust turbine including a first and a second scroll, an inline groupof four cylinders with a first cylinder fluidically communicating withthe first scroll of the exhaust turbine and remaining three cylindersfluidically communicating with the second scroll of the exhaust turbine.Further, a controller may be configured with computer readableinstructions stored on non-transitory memory for during a firstcondition, flowing exhaust from the first cylinder to the first scrollof the exhaust turbine and flowing exhaust from the remaining threecylinders to the second scroll of the exhaust turbine. Herein, the firstcondition may include high engine load conditions. Further, the firstscroll of the exhaust turbine may receive exhaust from the firstcylinder at 720 crank angle degree intervals, and wherein the secondscroll of the exhaust turbine may receive exhaust from the remainingthree cylinders at 240 crank angle degree intervals. The exhaust fromthe first cylinder may be received by the exhaust turbine approximatelymidway between exhaust received from two of the remaining threecylinders.

The controller may be further configured for during a second condition,deactivating the flowing of exhaust from the first cylinder to the firstscroll of the exhaust turbine and flowing exhaust from the remainingthree cylinders to the second scroll of the exhaust turbine. Herein, thesecond condition may include medium engine load conditions. In anotherexample, the second condition may include engine idling conditions.

The controller may be further configured for, during a third condition,activating the first cylinder, activating a first of the remaining threecylinders, and, deactivating a second and a third cylinder of theremaining three cylinders. Herein, exhaust may flow from the first ofthe remaining three cylinders to the second scroll and exhaust may flowfrom the first cylinder to the first scroll of the exhaust turbine.Further, the exhaust turbine may receive exhaust at 360 crank angledegree intervals. Further still, the third condition may include lowengine load conditions.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory. The specific routinesdescribed herein may represent one or more of any number of processingstrategies such as event-driven, interrupt-driven, multi-tasking,multi-threading, and the like. As such, various actions, operations,and/or functions illustrated may be performed in the sequenceillustrated, in parallel, or in some cases omitted. Likewise, the orderof processing is not necessarily required to achieve the features andadvantages of the example embodiments described herein, but is providedfor ease of illustration and description. One or more of the illustratedactions, operations and/or functions may be repeatedly performeddepending on the particular strategy being used. Further, the describedactions, operations and/or functions may graphically represent code tobe programmed into non-transitory memory of the computer readablestorage medium in the engine control system.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. A method for an engine, comprising: directing exhaust from a firstouter cylinder and a first inner cylinder of four cylinders to a firstscroll of a twin scroll turbocharger; directing exhaust from a secondouter cylinder and a second inner cylinder of the four cylinders to asecond scroll of the twin scroll turbocharger; and during a firstcondition, operating all cylinders with at least one uneven firing. 2.The method of claim 1, wherein firing events in the first outer cylinderand the first inner cylinder are separated by at least 360 crank angledegrees.
 3. The method of claim 2, wherein firing events in the secondouter cylinder and the second inner cylinder are separated by at least240 crank angle degrees.
 4. The method of claim 3, wherein operating allcylinders with at least one uneven firing includes firing the secondinner cylinder at 120 degrees of crank rotation after the first outercylinder is fired, firing the first inner cylinder 240 crank angledegrees after firing the second inner cylinder, firing the second outercylinder 240 crank angle degrees after firing the first inner cylinder,and firing the first outer cylinder 120 crank angle degrees after firingthe second outer cylinder, and wherein the first condition includes highengine load conditions.
 5. The method of claim 4, further comprisingduring a second condition, deactivating the first outer cylinder anddirecting exhaust only from first inner cylinder to the first scroll ofthe twin scroll turbocharger.
 6. The method of claim 5, wherein thesecond condition includes one of idling conditions or medium engine loadconditions.
 7. The method of claim 4, further comprising during a thirdcondition, deactivating the second outer cylinder and the second innercylinder.
 8. The method of claim 7, wherein the third condition includeslow engine load conditions.
 9. A system for an engine comprising: anintegrated exhaust manifold (IEM); an inline group of four cylinderswith two inner cylinders flanked by two outer cylinders, each cylinderfluidically communicating with one of four exhaust runners of the IEM,the exhaust runners of a first outer and a first inner cylinder merginginto a first plenum within the IEM, and the exhaust runners of a secondouter and a second inner cylinder merging into a second plenum withinthe IEM; a turbocharger with a twin scroll turbine, a first scroll ofthe turbine fluidically communicating with the first plenum but not thesecond plenum; and a second scroll of the turbine fluidicallycommunicating with the second plenum but not the first plenum.
 10. Thesystem of claim 9, wherein the first and second plenums are the onlyexhaust outlets of the IEM and do not fluidically communicate with eachother within the IEM.
 11. A method for an engine, comprising: flowingexhaust from a first outer cylinder of four cylinders to a first scrollof a twin scroll turbocharger; flowing exhaust from a first innercylinder, a second outer cylinder and a second inner cylinder of thefour cylinders to a second scroll of the twin scroll turbocharger, andduring a first condition, operating all cylinders with at least oneuneven firing.
 12. The method of claim 11, wherein operating allcylinders with uneven firing during the first condition furthercomprises firing each of the first inner cylinder, the second outercylinder and the second inner cylinder at 240 crank angle degreeintervals and firing the first outer cylinder approximately midwaybetween the firing of the second outer cylinder and the second innercylinder.
 13. The method of claim 12, wherein the first outer cylinderis fired at approximately 120 crank angle degrees after firing thesecond outer cylinder.
 14. The method of claim 12, wherein the firstcondition includes high engine load conditions.
 15. The method of claim11, further comprising during a second condition, deactivating the firstouter cylinder and operating all remaining cylinders, each with evenfiring with respect to each other.
 16. The method of claim 15, whereinoperating the engine with even firing includes firing each of the firstinner cylinder, the second outer cylinder and the second inner cylinderat 240 crank angle degree intervals, without firing the first outercylinder.
 17. The method of claim 15, wherein the second conditionincludes medium engine load conditions.
 18. The method of claim 15,wherein the second condition includes idling conditions.
 19. The methodof claim 15, further comprising during a third condition, deactivatingthe second outer cylinder and the second inner cylinder, and operatingthe engine in an even firing mode.
 20. The method of claim 19, whereinoperating the engine in the even firing mode includes firing the firstouter cylinder and the first inner cylinder at 360 crank angle degreeintervals, and wherein the third condition includes low engine loadconditions.